It's been suggested to get a hot-shoe bubble level for use with a ballhead tripod, when the camera doesn't offer a digital level (and the tripod head doesn't have its own).
Name brand levels, like this one from Manfrotto, cost over $30. In fact, even brands I haven't heard of cost that much. But generic models cost under $10 — Adorama's "house brand" is $6! Although that's just a single bubble, I've seen double-bubble levels for low prices in local stores.
Do I get better quality for the money? Am I just paying for the brand? If I save the $20, am I getting a deal, or am I actually wasting $10 on a level that isn't likely to actually be level?