A markup of over 3x is getting to be on the outrageous side, but on the very lowest end, a markup of 3x retail for something that may be serving 3 people is nearly a loss for the restaurant. So, on the dirt cheap end, I'd expect $5 a glass on the low end, or probably no less than $12 or so for a bottle. Note that Bronco Wine Co. (parent of 2 buck chuck and many many other wines) makes a restaurant versions of wine that aren't supposed to be available retail so you have nothing to compare it to. I've seen it sell in the $20s, and is probably not much more than $12 a case wholesale.

Often, the cheaper the stuff, the higher the markup (not always) and often, the 2d cheapest wine is the worst value, because people don't want to seem cheap, so they order the 2d cheapest one.