I may have misremembered about showing my passport at the machine; I was pretty tired at the time.
For me, beyond some of the things already mentioned by others, it’s role-playing game books and materials.
The rulebook(s) for D&D and other RPGs typically run for $25 to $50, and while there are tons of supplemental books that some publishers would like you to also buy, one might not actually need them. I have a lot of other materials (dice, miniatures, play mats), but most of those weren’t terribly expensive.
When you consider that an investment of $25 to $100 can yield dozens, to hundreds, of hours of game play, as well as time spent just gassing around with friends, the fun-per-dollar-spent number is really strong, at least for me.
There are several types still in use at various locations. The older ones need to have the passport inserted. The semi-newer ones don’t need that, but you do need to interact with its buttons & touchscreen and also adjust the camera’s angle depending on how tall you are.
All these flavors are still in use someplace. I’m just lucky that we have the newest whiz-bang ones where I happen to process through most often.
I buy 2-3 avocados every week (typically under $1.00/each from Kroger), so that I always have homemade guacamole on hand. Guacamole toast, guacamole chip dip, guacamole burger topping, guacamole fries, guacamole baked potatoes—you can’t have too much guacamole, I say. Heck, I even make guacamole hair gel when I want to look cool and fresh out on the town. 
For my wife and I, it has not been worth paying for since we cannot get the in-person interview.
I don’t know if we’ll score an interview before the application times out. Maybe my wife will since she flies internationally for work a few times a year and might get lucky…
Tea. I’m a big tea drinker, so much so that when I remodel my kitchen hopefully this summer I’m going to have a British 240v BS1363 plug installed at the counter to run a British-spec tea kettle which of course will heat up water much, much faster than the crappy American ones.
The tea itself, however, I’m not super picky. I stay away from total junk like Lipton or Red Rose but PG Tips or Tetley is fine for my weekday brew, and Twinings loose leaf Earl Grey is good on the weekends when I’m sitting on the back porch soaking up morning sunshine. A box of 80 Tetley tea bags is about $2.50 so that’s what, about 3 cents per serving? A box lasts me a month, so I’d say that’s the best bang for my buck(s).
Summerfest.
A music festival on the lakeshore in Milwaukee that hits the center of my Venn diagram:
Good Music/Outdoors/Almost Free.
They have a headliner every night that costs real money, but then there are twelve stages that are “free”… after a cheap daily ticket ($26, less for seniors, and FREE most afternoons with daily promotions).
Oh, those dozen stages are filled with over a thousand bands, to the extent that you have to make some tough choices (Sat. 6/24 has Elvis Costello with Nick Lowe and Vanilla Fudge on before him, Lyle Lovett, Nitty Gritty Dirt Band, Wishbone Ash, and Willy Porter with Biff Bleufamgagne… luckily, my ADD makes it easy to saunter back and forth between stages).
Check it out…
Another one: video games. I’m not a huge gamer – I grew up in the SNES generation – but I’m slowly becoming more interested in playing video games as I’ve gotten older (I think finishing my MA killed my desire to read books, a desire that used to be insatiable). During the height of the pandemic stay-at-home orders in spring 2020 I bought a used Switch for $60 which came with Breath of the Wild, and a friend gave me Animal Crossing. Between the two of them I’ve spent thousands of hours playing, and now that Tears of the Kingdom is out I suspect I’ll spend hundreds more. So, $60 for the Switch and $69 for TotK,… a damn good return on investment.
When I decided to get the TSA Pre-Check I remember being concerned about being able to get the in-person interview. TSA had an office at Raleigh-Durham, but since I don’t drive I had a choice of making a special trip to the airport just for the interview, or try to get it while I was there for a flight. As I recall, when I tried to schedule one there wasn’t one available, but it said they do have walk-ins. So one of the times I was going to be flying I made a point of getting to the airport early. After checking my bag I went to the TSA office to see how long I would have to wait for the interview. I had previously done the paperwork and brought all my documents, so I was hopeful. The agent gave me an estimated wait time which would allow me to catch my flight.
So I took a seat in the waiting area, and made a point of keeping an eye on the time. (Fortunately, I had one of those airline-assigned pre-checks, so I knew I wasn’t going to have to wait long at security.) They called me in with plenty of time to do the interview, so I didn’t have to do a mad dash through the airport to make my flight. While I was out of town I got the notice that my application had been approved, so I had it for the trip home.
I think it was back in about 1998 that I purchased a CD of Hoyle Card Games for Windows. It cost me about 8 bucks. I played those card games for years, using the same CD loaded on multiple PCs on multiple versions of Windows. I shudder to think of how many hours I played against players like Jasper and Roswell and Elayne and Harley. I quit playing Hoyle only when I discovered better online sites. But it was certainly 8 dollars well spent.
Heh. I had a CD-ROM version of Boggle that both I and my SO played the hell out of for years. Unfortunately I could never get it to work with any post-XP version of Windows, and I’ve never found a satisfactory substitute.
At about that same point in time, a friend of mine gave me PaintShop Pro, a graphics-editing software package. I’ve likely installed it on, and used it on, seven or eight of my home PCs in the past 25 years; it’s run just fine on every version of Windows I’ve had, and for the fairly rudimentary stuff I do with pictures, it works brilliantly.
Given that I paid nothing for it, and have gotten a quarter-century of regular use out of it, the price/value has been amazing. 
JASC PaintShopPro? I bought a copy years ago, then got an upgrade to the newer version for about $10. You’re right…it works perfectly on every version of Windows. I use it at least once every couple weeks. Over the period I’ve had it, it’s probably cost me less than $3.00/year.
Wanna buy another? I’ll make you a super deal!
I loved to buy a cheap piece of electrical/computer equipment at a thrift store, fix it up, play with it, etc.
There have been several items I bought for <$10 that provided untold hours of joy in this regard. E.g., a couple of disk drives for $3 each that were labeled as non-working but just had the jumpers set wrong. More than doubled my storage space at the time. A Sony SuperBeta for very little that worked just fine, used for a while and sold for real money. And on and on.
But those days are gone. The thrift stores know the value of these things now and some have deals with computer makers to “recycle” (i.e, throw out) computers rather than resell them.
Another weird thing is old 386/486 type boxes are selling for big bucks on line. Vintage computers are that hot. E.g., I saw a no-name 386 box today at auction selling for over $200. I’ve thrown out a dozen of similar systems over the years. I had my “bang” with those things but they were taking up space and I certainly wasn’t going to move with them. Could have bought something nice if I could have sold them for that kind of money, doubling my bang.
That’s the one! I have version 5.01, with a 1998 copyright on it.
This is likely a niche one, but I offer music camps.
I play bluegrass/oldtime music on upright bass and clawhammer banjo. There are any number of “camps” which you can attend and study/eat/hang out with worldclass musicians. And when I say worldclass, I mean the absolute TOP players on their instruments. For example, last year I was one of 6 bassists studying w/ Paul Kowert and Todd Phillips. Doesn’t get any better than that. If the names mean nothing to you, it is the same thing as if you liked baseball a camp where you hung out with last year’s MVP and Cy Young winner - or at least a couple of the starters on your favorite team.
This year I’m going to 2, a banjo camp next week, and a bass camp in Oct. Both are about a 3 hr drive, and with food and lodging cost around $800. From Thurs thru Sun, you get to hear the pros play, jam with them all night long, take lessons from them, eat meals with them, then wake up the next day and do it all over again!
I have outfitted more than one small business from these folks:
I used to live nearby; they’re good people with a solid rep.
They buy whole corporations-full of old PCs, refurbish them, and sell them by the 1 or 2 or by the one or two hundred. Whole systems or just bits & pieces and chunks. They’re mostly the corporate models, not consumer models. So rather more reliable / rugged. A 5yo machine may have 10 reliable years left in it.
Kid: meet candy store. 
I’m privileged to have PSP 8.0…released in 2003. I think that I paid $39.95 for the original and $10.00 for the upgrade.
There are some things that are just inherently funny (a Mazda’s wankel engine, calling someone persnickety or luminescent, words like cattywampus or dongle, eating figgy duff or a bowl of kumquats)…
Sorry for the tangent, but I thought you should know that I will be trying to fit “Banjo Camp” into a conversation this weekend.