For a historic perspective, see the discussion of “quality control” in this article:
Truly high end cars parallel park for your driver. 
I remember one of the guys on Top Gear said that if you want to know what features will be in your car in ten or fifteen years, look at the current-day Mercedes S-Class.
This is now a federal requirement for all new cars manufactured or sold in the US since May 2018. Hardly a luxury feature.
On my wife’s Infiniti, all of the internal settings (driver’s seat position, steering wheel position, side mirror position, favorited audio stations, etc.) are triggered off of which key fob is in the drivers area. So when I’m driving it automatically switches to the settings of the fob in my pocket. When she drives, it switches to the settings per the fob in her purse.
My wife’s Tesla will pull in the side mirrors 25 feet before she gets to the garage. And opens the garage door when she gets close. (and closes it when she drives away). She makes fun of me when I have to push a button to open the garage. 
Other features I’ve never had before. Both our cars have phone apps that allow us to lock doors, check charge level, etc.
My iPace has ambient lighting, and I can change the color and intensity. It also has a light that projects down from the side mirrors at night so you can see the ground as you step out (It also projects the Jaguar logo).
The Tesla has a built in dash cam (front, sides, and back)
It also has sensors so the doors won’t hit something if you open them near another car or a wall. You can open and close any (or all) doors with a push of a button.
I’ve been super-fortunate in my life, and have owned a number of luxury or performance cars. Several BMWs and Audis, an Infiniti, an Acura, a Lotus. In that same run of cars, I’ve also owned a Ford, a Honda and a Chevy.
Much of what has already been said seems right to me. In the more expensive cars, every touch point has been of nicer materials, the seats have been better, the controls more intuitive and solid feeling, and things like the displays, the cameras, the software have all been crisper, higher-res, easier to use, less likely to get hung up or slow to respond. Suspensions have been better, and where the engines might be shared, the ECU maps have been tuned for more performance and the mounts and other drivetrain components have allowed less vibration and harshness through.
Well, all except the Lotus. That was an aluminum ashtray with a go-kart motor bolted behind the driver’s seat. But as designed and expected.
What I noticed above and beyond all that was the dealership and service experience. The Honda and Chevy dealerships were pure stereotypical sweatbox environments. Let me go talk to my manager, we’d never offer this deal to anyone else, what payment can you afford, are you sure you don’t want the Tru-Coat type bullshit.
The BMW, Audi and Acura dealers were nothing like that. The showrooms, offices and waiting areas were much more comfortable with good coffee, snacks and other drinks freely available. The pressure to buy was much less, more of a professional business deal than a squeeze play. The service departments were more flexible with sooner appointments, always had loaners and not the shuttle, would do things like come and get my car sometimes. Just an all-around better experience.
And my wife just picked up her new Tesla last week. That was even better, if not really directly comparable. But that feels like a bit of a hijack so I’ll leave it at that for now.
Most of what I was going to say has already been said, but I will add that once you move beyond the “mainstream” luxury brands like Lexus and Cadillac, and move up to the ultra-luxury brands like Rolls-Royce or Maybach, you start to get some ridiculous ultra-luxury features. Like a champagne chiller in the back seat, with special champagne flutes that come with the car, and special cup holders for the champagne flutes. And an entertainment system for the rear seat passengers (although admittedly that’s a feature you can get some some minivans as well). The assumption is clearly that the owner will be sitting in the back seat sipping champagne and watching TV, while the chauffeur drives.
Oh, and the quality of materials. My understanding is that there is literally no plastic whatsoever in a Rolls. Everything is either metal, wood, or leather. And the carpet is extremely thick and plush. Although as I typed that it’s pretty obvious that carpet is neither wood nor leather, nor metal, so that obviously contradicts my previous statement. But it’s at least plausible that they use some expensive natural material for the carpet rather than the synthetic stuff you’d find everywhere else.
While a lot of the “tech” items have quickly trickled down to lower spec’d vehicles due to their lower marginal cost and in many cases safety requirements, there’s still plenty of differences. 360-degree camera systems are still pretty limited because of the number of cameras required to make them work. The quality of materials, switches, knobs, levers, leather, etc. is a huge differentiator. Aluminum, stainless steel, hand-stitched leather, lacquered wood, hand-painted decals and trimming, engines with signed builder certifications. Those heated and cooled storage areas are still pretty hard to come by.
There’s also heft. Everything on luxury cars just feels much more substantial and heavy, because usually it is. There’s much more and better insulation to eliminate road and wind noise, which matters when you’re streaming movies to the touchscreen(s) in the rear of the car. Heated seats are so last millennium, even heated and cooled (not just ventilated) seats are becoming quite common. True luxury means heated/cooled and massaging seats, front AND back. There’s power-actuated, if not fully power-operated doors, and tailgates for SUVs.
Look up some of Doug DeMuro’s luxury car videos on YouTube, he points out all the absurd and not so absurd luxuries you can get these days.
I was always fond of pointing out to people that bought a Lexus that they bought a Toyota with leather seats.
Cadillac and Lincoln were the worst offenders in my view. (ever drive a Cimarron?) GM seems to have done a better Job rebranding Cadillac.
But to me a true luxury car was always Mercedes/BMW type companies (ignoring ultra luxury like Rolls Royce which i would put in a separate category). Thats all they made. The auto industry has had a lot of consolidation over the years and i’m not an expert car guy, but i still feel that way.
A lot of good points have been made about quality of materials, availability of higher end extras, and so forth.
But being the thrifty guy i am, i’d get a Toyota with all the bells and whistles if i just wanted a very nice reliable car.
I drive a 2013 Mazda 3 hatchback with the top trim package (Grand Touring). My previous car was a 2004 Mazda 3 hatchback with the top trim package (Grand Touring) so I have a pretty good perspective on how the bells & whistles trickle down on a pair of cars that are about as similar as possible except for a nine year difference in age. And the new (8 year old) car has just loads of things that the old one didn’t have:
fantastic traction control,
blindspot monitoring,
in-dash nav & infotainment stuff like integrated satellite radio,
dual zone climate control,
dual heated seats,
headlights that ‘look’ in the direction of travel,
power seats,
keyless entry & start,
rain sensing wipers.
I mentioned this, but they were basically the same for whatever year I looked. But that’s irrelevant now, they apparently killed the Land Cruiser finally.
The new J300 model isn’t going to the US, but it is otherwise quite alive. According to Wikipedea Toyota sells five times as many units in Australia as the entire USA. Pretty clear where they will put their efforts.
Yes, meant US market. They’re big in Central Asia too.
I would admit to a certain psychological difference: I’d feel better using them the way they are intended (off-road) if it’s a Toyota. Just seems weird to muddy up that Lexus, even if illogical.
My 1996 Mercedes has the same feature…but then again, it’s a Merc.
Doug DeMuro’s videos are exactly how I learned there are cars that come with their own champagne flutes.
It’s pure wool. Wilton wool.
You mean yours doesn’t come with them? Pfft
I find it hard to believe there isn’t any plastic at all but you’d probably have to go looking for it. And there’s quite a but of rubber on car for tires, hoses, seals & weather stripping, speaker surrounds, possibly noise reduction material, etc. And glass. And copper wire. And whatever is under the leather seats.
And actually plastic is an excellent material for certain purposes. So even if it’s true it would be counter-productive in some respects.
Pretty much this. The fit and finish can be a big difference. GM seems to have a big problem with this. Even their high-end cars seems to have chintzy knobs and lame, unintuitive and ugly screens and whatnot. Like they invented one standard and put it in everything.
Also, the highest end cars will have things like better cruise control (lane assist, adjustable speed [keeps a certain distance from the car in front of you without your input]).
You also may see better performance in luxury cars (more powerful engines).
For example, the Audi RS6 is a station wagon that can do 0-60 in 3.6 seconds. Madness. Costs $120,000. Also madness.