Mushrooms here are pretty cheap, but mushroom aficionados would probably find the everyday supermarket’s selection rather pedestrian - white ones, brown ones, portabella, shiitake, and a pre-sliced mix of “gourmet” mushrooms (all of those mixed together) is about it. For someone like me, I think they should whittle that down a bit and stock something else I’d prefer to eat!
Anything beyond that, and it’s off to the gourmet shop, where instead of $2/pound, they’re more like $10/pound (I think…I haven’t bought any for ages).