In store, it’s hard to tell the difference. They run in a ”Store” / “Retail” mode that amps up the brightness and color saturation to a level that’s often unsustainable (it will damage the TV if you use it in this mode) and that doesn’t translate well to actual content because it’s too vivid.

If you’re interested in understanding more about modern TV technology / which TVs are best, I recommend checking out Rtings and HDTVTest (there’s a site, a channel on Youtube, a subreddit, etc). The former because the reviews are great; the latter because Vincent explains these things well. He talks about specific technologies like types of OLED panels, different LED technologies, different settings on TVs and what they mean, calibration, etc…

To answer your question, though: the more expensive technologies are what cost the most, and bigger versions (starting at 55”) also tend to cost more. Right now the best TVs you can buy are OLEDs - specifically, QD-OLEDs like the Sony A95L. A 55” is like $2500. By comparison, a traditional OLED (or “WOLED”) like the LG C3 is half the price - a 55” is $1300 - and nearly as good. (And a previous gen model, like the C2, will be even cheaper, if you can find one.)