I was surprised, because I was assuming that either the no-limit would raise conversion so high that it would win, or that just keeping the threshold high, which would keep the average order value high, would win. I didn't expect the middle.

Fifty dollars is conservative. The 'powers that be' worry about giving away something and not getting enough in return.

The key was how little effort it was to actually learn something and be able to apply that learning on the fly. We applied the learning later that week for a nice surplus. And it took all of a couple hours work.