Would think shop=discount_store would best differentiate between "shops with lots of variety" and "shops with cheap goods" which may not be the same. E.g. a bodega would be a shop with variety, but not necessarily all cheap.
Also, I suggest a key, say fixed_price=*, which could indicate the standard price of the objects. E.g. for a 100yen store it would be 100 yen, dollar store 1 dollar, and so forth. (And those odd cases where a 100 yen store is located in the US and it becomes a $1.50 store...) - KTyler 01:14, 9 June 2012 (BST)