There's probably a handful of sticky ethical and legal issues surrounding the potential sale of things I make on the Microsoft campus.
In any case, the delrin hub is really an absurd design choice. The rods for each of the EPDM rollers are only 1/8" diameter pins as I mentioned and milling a slot for those on the milling machine just makes me nervous. It's not impossible, I know, but I can only guess how many endmills I'd break while trying to do it. By using delrin, we're able to use a reasonably strong alternative to aluminum, but to do so much more quickly and easily by using the laser cutter. The downside is that delrin is far more expensive. So, even if it's more prone to breaking, we can replace the delrin parts in a heartbeat. It's not a bad compromise, I guess.