Heh, I've been through this upgrade frenzy too, from msrp $240 to msrp $1100 bikes. You really do get what you pay for, but right off the bat at about $200 you get roughly the equal to wal-marts finest, but with better assembly, service, and support (the top end schwinn hardtail there is actually pretty decent if you know how to properly assemble it yourself, about equal to a DDB outlook). Once you hit 240, your aboves what walmart offers at a hardware level as well. About 350 you start seeing upgraded components, and sometimes lighter frames.....around 400 you start seeing disc brakes at teh cost of component groups.
at 500, you start seeing only lightweight frames, lx (and sometimes XT) components, good forks, light wheelsets....basically if you look across every companies lienup there will be some very nice parts. once you hit 600....the bikes are usually pretty much decked out. 800 can land you a bike like my talus, which is pretty much a killer XC frame with a rather nice component selection (frame only is availible). Retail on it is 1100, but bay area cycles was selling one for about 800...so remeber never pay retail unless you absolutely must have it "right now".