Also, lots of older languages demand higher pay due to the small applicant pool. I know Cobol and Fortan in banking / finance devs making 400k plus bonuses and saw a K / kdb+ job that was offering 500k. Hell, I even know someone getting paid to write and maintain sql sprocs! Obviously these are anecdotal and not ubiquitous but the job market is a really funny thing when you get into esoteric knowledge.