Yes every allegiance has a price , however What you're suggesting from what i understood is that A16z would pay 50 million dollars to a new hire. With them being in the VC business , i think they know that , such amount of money can possibly invested in growing their portfolios.
I don't have any evidence of any engineer being offered such exorbitant salaries , however this gets close.
Ok, it's somewhat of a hyperbole. 50M for a single hire is extremely exorbitant (after all, we're not european soccer players), but consider being offered a salary 5 times your current pay.
I'm loyal to my employer as hell, even though he only pays me around 45k (euros, yes, i should get more ;) and I'd like to think I'm 'morally gifted', so I wouldn't consider quitting my current job when someone offers me double... 3 times plus, is a different story, I'm scratch my head at least twice.
I'll retract my statement if someone shows me real evidence that they've turned down a 500 (ok, perhaps 50 should be enough) million dollar job offer.