From their website:
Errors on Our Site
Prices and availability of products and services are subject to change without notice. Errors will be corrected where discovered, and Best Buy reserves the right to revoke any stated offer and to correct any errors, inaccuracies or omissions including after an order has been submitted and whether or not the order has been confirmed and your credit card charged. If your credit card has already been charged for the purchase and your order is cancelled, Best Buy will issue a credit to your credit card account in the amount of the charge. Individual bank policies will dictate when this amount is credited to your account. If you are not fully satisfied with your purchase, you may return it in accordance with Best Buy's Return Policy.
Using Digital Coupons
Digital Coupons, unlike credit or debit cards, are debited at the time an order is placed. Digital Coupons will automatically be redeemed to purchase totals, up to the total purchase amount. Digital Coupons must be used prior to their noted expiration date and within a single transaction. Coupon cannot be replaced if it is lost, stolen, deleted, or if you cancel or return your purchase. In the event of a reduction in price below the coupon value, the excess value of the coupon will not be refunded. For more information, see Digital Coupons in our Help section and review details of each respective Digital Coupon offer.
Best Buy Bucks™ are valid for one-time use only and must be used only during normal hours of operation in Best Buy™ stores located in the U.S. between 10/3/06 and 12/2/06 OR at BestBuy.com® between 12:00:01 a.m. (CT) 10/3/06 and 11:59:59 p.m. (CT) 12/2/06. Best Buy Bucks™ may be combined and the cumulative total will be subtracted from total purchase amount of merchandise before the calculation of sales and similar taxes. To complete the transaction, you will be responsible for paying any amount owed after the redemption of Best Buy Bucks™. If the transaction is cancelled or merchandise is returned for any reason, all Best Buy Bucks™ redeemed during such transaction will be forfeited and deducted from the total purchase amount of the merchandise, and you will receive refund or credit for the balance only, if any (subject to Best Buy's standard return policy). If merchandise is returned for exchange, all Best Buy Bucks™ redeemed during such transaction will be applied to the exchange transaction (subject to Best Buy's standard return policy). Value of Best Buy Bucks™ may be enhanced for the purchase of select products or services featured in special Best Buy promotions (subject to these Terms & Conditions).
**************Sure, sue them*****************