I'll second the Wisconsin standbys. Up until 2 years ago I could get returnable cases of Leinenkugels COLD for $11. Used to like PBR on tap for the price, but now that they sponsor rock concerts, that's not true always. Minnesota Premium Grain Belt is good, but I've heard the brewery was sold, and the water no longer comes from the artesian well in Minneapolis, making it not as good.

Also recall Rheinlander 10 packs of bottles for $3, but it wasn't _good_
We also would get the Meister Brau returnable cases for $6, icky as well. The store kept it under the produce coolers where it was WARM from the exhaust.

Current favorite is Huber Bock 12 packs of bottles for $6. They used to sell the returnable cases for $8, but alas, they've been acquired by a Canadian Malt Liquor mogul, so I'm sure that will not help. Huber ranks higher in taste tests than their flagship Berghoff Bock which costs more, but is still good.