FWIW, I used to work in the mail order business in a different industry. It's not atypical for stores to charge tax and there's nothing wrong with it - so long as the tax money actually does get to their state government. It's just that currently there's no law forcing them to charge interstate tax. They've done nothing "wrong," per se, but it certainly doesn't meet client expectations for many in the mail order industry.
A few other things - denying the credit card charge may or may not be helpful. On the one hand, the contract was not complete until you agreed to the terms of the contract. However, there is very likely an exception built into Utah law that says that the buyer implicitly agrees to pay sales tax in addition to whatever the total is on the bill. In fact, if they find out for some reason that you should have paid sales tax on a transaction and you haven't, the state can legally come back to you (via the store) and demand it. The credit card companies know that, and if the source of your dispute is that you received the goods but they over charged re: sales tax, your claim will likely die on the vine.
As for the credit card v. cash issue, they obviously pay a fee to accept your credit card. That fee probably eats substantially into whatever the commission or bonus the guys at the store make. It's not unusual in a small store for that fee to be 2.5 to 3%. Already getting 40% off, however, it sounds like you got a close-out. They may have effectively sold you this bike for at cost or slightly more than. That 2.5 to 3% may have been their entire profit on the deal. Can't be surprised they'd take that approach. But for reference, they can't charge you extra to accept a credit card - nor can they deny you the right to pay that way. They CAN, however, offer a "cash discount."
Hope this is useful for the next substantial transaction if nothing else.
Last edited by Nika Aldrich; 06-02-07 at 12:28 AM.