There's this belief here that Wal-Mart only sells sub $200 bikes. While I can't attest to the quality of them, a gander at their website reveals that they do sell some bikes in the $500 to $800 range--mostly Schwinns, KHS and the like. While not comparable to "high-end" $1000 bikes, one would assume these 500-800 dollar bikes have better components than their $100 cheapies.
For my budget, anything above $500 would be a pretty pricey purchase.