The Robinson Absolute pinions are hardened, so they do last a long time, and run about $5 each. I have several that have been around for ages. That said, I much prefer the Losi pinions. They are hands down my favorites.
The "standard" Robinson pinions I would recommend to no one. Even with proper slipper adjustment and gear mesh, they'll be sawblades within a matter of 8-10 packs. They just can't withstand brushless power.
There are no atheists in the foxholes / There is no intellect in the air / There are no scientists on the way down / Just a working example of faith versus physics. --El-P, Flyentology