Graphite costs $25/month per user and there's no free tier I can use on enterprise. No matter what productivity gains I might derive from Graphite, I will never be able to convince my boss to pay for it, just because there's no way to prove that said gains exist.
And because there's no individual tier, I couldn't pay for it myself if I wanted to. Honestly, I would if I was forced to switch to GitHub, because stacking on Gerrit has increased my productivity by 2x as I'm no longer blocked on code reviews. Even a tiny pay gain because I'm now a top performer is worth the $25/month to me.