law-suit
Actually...
Companies (stores, businesses without a signed contract, and such), can change the price at anytime they wish up to the point where they actually possess your money.
The advertisment of a price is not a contract in and of itself, it is called an "offer" in legal terms. An offer does not constitute a contract...it is simply an "offer."
Now, it is obviously poor customer-service to change the advertised price, but the U.S. courts have upheld this concept time and time again. It protects businesses from mis-prints in ads as well as protecting them when they are in the process of "changing" the prices (whether it be with a price-gun or in a computer system).
Even if you make your order, if they (in this case, buy.com) realize that the price was incorrect, they can change the price...they are obligated to let you know they have done this and allow you to cancel your order, but that is the extent of your obligation.
I've been on all three sides of this as a retail store manager, consumer and lawyer.
Like I said, it's bad customer-service, but they are o.k. legally.
Aaron