Their rails are only 8' long? If they're charging that much, it should be a whole damn mini park and a drop in!
Adjustable length legs are cool though. I might have to build those for my next pvc rail.
And to OP: recycled pvc, wood, and other building materials are pretty cheap, and setups are fun to build and customize for your own enjoyment. It's a lot more fun riding something you've built than bought.
I will say mSnow is worth the money for surfacing a drop in though! It's turned out to be reasonably fast, and provides crucial edge hold for practicing 2's on. Much nicer than plastic lattice, carpet, or turf.