I am going to repeat my usual rant about bags for the umpteenth time - cheap bags are a waste of money in the long run. The best alternative is a used name brand bag (and NO, Wal-Mart is not a name brand bag seller). You will or should pay about half retail, good bags are for sale almost everywhere, and well worth the money. Example - I have a Marmot down bag I bought last year in virtually new condition (even had the original hang tag and both stuff and storage sacks) for half retail ($200 compared to $400).

PS, some people don't like the idea of buying a used bag. A trip to the cleaners solves that issue, at least for me. Also, see that parka I'm wearing? Also half price on eBay (retail was around $500 and the new version now sells for $600). It looked brand new when I opened the box.