I know there should be big difference between various countries.
A developer with two years of experience in China may earn 15,000 a month(21.75 days), or 86 RMB (~12.5 USD) an hour (8 hours a day).
The best blockchain developers can't be bought -- and certainly not by the hour.

Best blockchain devs have many bitcoins, like Gavin, he has more than 10000 BTC, why he works for others for normal rates? He doesn't need to work any more and coding is his hobby, maybe he will work as a CTO or co-founder in blockchain startup.