at my local pet store, it depends on a few things.
1) who's working
2) tail type
if the cool guy's working, he sets them up all fancy. HMs and other fancier bettas are placed in containers, like the divided half-gallon hex-thingie without the divider, set up in nicely decorated bowls, ect.
the HMs are usually in bowls, anyways, because they sell faster, and i guess people like the ways the bowls are decorated? not too sure.
if they have alot of bettas come in, the VTs get to live out their life while at the pet store in the tanks in back, with friendly fish. if they only get a few in, or it's mostly VTs, they stay in the cups.