Keeping a car clean through winter slush and spring mud is a constant battle, and factory mats just don't cut it. A solid set of custom-fit floor mats and a trunk liner usually run about $250, which is a fair price to save your carpet from permanent salt stains and spilled gear. Prices on these tend to dip right at the end of winter when retailers clear out inventory, or during major holiday sales in November.
When you're buying car accessories, you want to separate the purchase price from how you pay for it. If you need to spread out the cost, a financing window can help, but don't expect a plastic liner to discount itself just because you have a credit card in your hand.
That intro window is a deadline, not free money, so make sure the balance is fully paid off before the 18 months are up or you'll get hit with the accumulated interest.