Since it seems to have been the least popular of the "large" expansions, why do people think this?
eBay has a lot of new Carcassonne Catapult's right now! Not sure what you consider a reasonable price but the least expensive one for is for $64 with free shipping.
Don't know what shipping is to US, but several other older expansions are still available there.
Started by SRBO
Started by blaice
Started by Whaleyland
Started by Halfling