So I've been browsing EBay for a while, looking at seat covers and such for my Mustang (got the tan-colored interior. Though it looks pretty good, it gets dirty easily and I already have some stains on the seats.) Last week I saw an auction for a set of tan-colored seat cover take-offs (including front, back and head rest cover). The surprise is that the starting bid was $9.99!
I bid on it and won it for $9.99. Turns out the shipping was $28. I thought it was a bit expensive for shipment, but it was still a good deal. I just got it today. Turns out it was a 4-5 foot tall box (that's why it had the high shipment price.) The seats included all the foam guts and everything, and are in pretty good condition!
Now it's just a matter of deciding how long I want to keep my current ones before replacing them. Might wait another year maybe.

 

Might be worth it to keep them in the box if you intend on selling the car, then replace them at that point. You'll get them stained again in another year. Or buy a third set...

 

Good idea.