"I don't know a single person who is proficient at Solidity for more than a year and a half that isn't a millionaire." - Griff Green

Griff Green is a philanthropist and Ethereum developer. Solidity is the only coding language he knows and he is presumably, based on his statement and his history in cryptos, a millionaire.

SOLIDITY was released less than 3 years ago and is currently the most common/main language for Ethereum contracts.