If you're only interested in "clicking to buy" a stripped lower, like you'd click to buy a video card, you're probably not going to get one. If you really want one right now, you need to call around to your local gun stores first, then one or all of the many vendors people posted and ask if they're in stock; if that is too much work, you're probably SOL. Remember unlike buying a computer part or anything else, most gun stores are small businesses, most of the business owners are hobbyists like you and I; and they're generally going to be good people to deal with. I always say check your local stores first, because they support your local economy. Personally, I'd rather pay a bit more to buy something from a local store than from any place out of state... because the money stays closer to home.
500grains, what's the URL for Gunsmoke?
The stores local to me are gouging just as bad as the folks on the auction sites. Mail order seems to be the way to spend the least amount of cash on your build.