By Daniel Kline Discount carrier Spirit Air offers low fares, but those come with a heavy price that may not be worth paying. Spirit Airlines (SAVE) – Get Spirit Airlines Inc. Report offers a fairly simple proposition: Customers pay very low prices but get little other than seats — and not specific ones — on the planes. Everything from a carry-on bag to the opportunity to choose a seat costs more, and it’s all a la carte. Technically, if you want to fly with only a small personal item and are willing to wait for the last available seat, you can fly on Spirit for just the price of a ticket. T…