I don’t think anybody’s going to be giving up their full FRC field border if they’ve got one. Unless they’re losing the space for it permanently.
Carpet, on the other hand, you may not need to purchase. I’m not 100% sure if this applies to FiT, but at regionals if you want the carpet afterwards you notify the Regional Director (Program Delivery Partner) ahead of time and show up with a vehicle that can haul it during field takedown.
Or you can do what we did once and get a bunch of people to lift it and tie it to the roof of a mentor’s car. Then smash their side-view mirror when you try to unload it by rolling it off. Not recommended, but technically an option.
Your best bet to not pay the ridiculous carpet prices would probably be to snag one after an event teardown. Generally they just dump the carpet so if you want it they’ll just hand it off. I would check with TRI staff beforehand to see if you could possibly claim it.