Not to sound offensive , but you're not A16z.
1.<< A16Z is rich enough to buy people>> No one is rich enough to buy people , unless well if you're talking about criminals.
2.Most good engineers will tell you , that money is NOT the primary motivator for them to build great products.( So aqui-hiring won't work)
3. As for Hackerrank--> that's what they're supposed to do - find people with good technical skills.
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.