Cheap standby flights -- still a thing?

Indeed. As I said a couple of years ago, on this board:

Note that I was not picking on Expedia; I was just using them as an example of a comparison travel site.

I still say that it pays to pick up the phone and speak with a live booking agent (there should not be a fee for this; they want your business, after all); or if you must book online, to read the fine print that is usually linked to the fare. If I check flights from, say, Calgary to Toronto on Air Canada online, I get five or six fares, all linked to what they provide (for example, free checked baggage, first checked bag at $25, food and beverage included, food and beverage paid for onboard, wider seat, more legroom, etc.). As a result, I am never surprised at what I get.