Too pvc pipe and cut holes in them and then bought cheap jump cups from horse.com, capped the standards with caps and used toilet bottoms (pvc) to attach to wood bottoms (used a 2 X 8 and cut it up). And then bought 2" pvc pipe and cut it in two. Everything came out to about $100 for 6 jumps. Sorry, no photos.
At the show I was at recently it looked like the jumps were simply PVC pipes, joints (4 of the simple ones like one corner of a square, and 2 T joints), jump cups (no idea where to get those) and... colored duct tape. I imagine the PVC uprights had holes to move the jump cups up and down.
Granted, I wasn't right there beside them,but it was just a square base with the uprights coming off them at a T post junction.