So what is cheap beer? Is it mass marketed brew? Is it something typically priced under Bud, Miller and Coors products? Or can it be just what's on sale?
I think cheap beer can be all these things. I recently made a stop at one of my favorite places for cheep beer: Kenwood Liquors at 10750 S. Cicero Ave., in Oak Lawn, IL. If your in the area it's a great place for super-cheap southside beer -- you've got the likes of Bud, Miller and Coors (for quite cheap) as well as your other second-tier cheap beers such as Old Milwaukee, Milwaukee's Best, Keystone, etc. Kenwood is one of the few places left you can find Ballantine Ale. It's only available in 40-ounce bottles and only at certain times of the year. The last time I was at Kenwood I didn't see it, but when it's available, it can be had for a little more than $2 for a 40. Not bad at all.
Ballantine is cheap, but it's a beer with a long history that is well documented by John Smallshaw. He provides a pretty thorough history of Ballantine's one of the last surving historical American ales. The beer has lost some character through the years, but I believe it stil has an edge over other beers at the same price. It's also a great introduction to ales if you mostly drink macro-brewed lagers.
If you're at Kenwood and if you like better beer and don't spend that much you're in luck. There are usually a few microbrews to be found cheaper than you'd ever think possible. I recently found Ruedrich's Red Seal for quite cheap at $5.62 a six-pack. I normally see this beer for between $7-$8 a six. If you're interested in better beer, such as microbrews and imports, check out the Marcobrau Beer Pages. Meanwhile, I'll be looking for some Ballantine's.