How much is $630 worth? According to The Register the rather surprising answer is $714. That is the price that an enterprising eBayer has put on some money, and by manipulating the Microsoft Live Search advertising cashback offer implemented by Microsoft last month the guy reckons you can turn a profit when you buy.

The theory being that accessing the purchase page via a special Love Search advertising link, which promises 35 percent cashback (direct from the advertiser) on the purchase price, you get back more than the $84 premium you've paid. In fact, everyone wins - except Microsoft and eBay it seems.

El Reg has not managed to get anyone from either company to comment, nor has it actually tried to buy $630 in order to test the theory either.

The loophole in the cashback scheme itself was exposed by FatWallet who noted that the eBay purchase has to be a buy it now option and paid for via PayPal in order to work. I have a funny feeling that if it did work before, after The Register story it certainly won't be working now.