Companies would be smart to chuck in 10% bonus after a year, 20 after 2 etc. to 50 after 5 and lock that in at hiring time. Like you say: domain knowledge. You would end up with smaller more productive and happy teams. In addition pay increases to market.

Asking too much? “Waaah! It is really hard to find good developers” is a stuck record on loop since 2016 at least