I'm not saying the Tormach fan is any better than the ebay fan. But there can be a very large difference between cheap fans and expensive ones. BB vs sleeve bearing, and quality of ball bearing. Fan shape affects noise significantly.
My Series 1 tormach case fan died a noisy death, and I replaced it with a local electronic shop fan. Seems to be working.
Now my computer fan is making horrible noises. (not Tormach)