There's also the saying, "No risk, no reward". Most of the receivers (if not all) they sell are refurbished, hence the price difference. Of course buying a refurbished product is a risk, but in my experience, I've been fortunate enough to have very good success with places like eCost and uBid with refurbished products.
Personally, I take online rating and feedback with a grain of salt. It might give you an idea, but it's also open to undue praise or negativity, as there's little to no safeguards on validation of this information.
To each his/her own, maybe worth it to some, may not to others... -TD