Matters what you're using the language for more than which language is being used I would imagine.

Scala users make more than .NET users, but that isn't because Scala is more in-demand, it's because that's the language of choice for a lot of Machine Learning / Big Data folks using spark who are highly sought after. I would bet that average Scala and Java compensation is very different, with Scala being much higher, due to the Java average compensations getting watered down by salaries of Java developers that just make CRUD applications but at the top of the scale they're likely similar and they both map back to Spark developers that are Machine Learning / Data Scientist / Big Data engineers.

Same with SQL- in general it isn't highly compensated because "everyone" knows/uses SQL (rarely well, though)- however there are also tons of Data Engineers whose core competency is SQL and they make great money.

You think? A huge chunk of work at Google is Java.

I don’t think that’s well specified enough to measure. But assuming you mean something like median comp of a job that requires X, I’d imagine the top of the list would all be things that are pretty obscure.

Suppose there’s one hedge fund that wants an expert in k and is willing to pay whatever it takes. Does that mean people should go out and learn k?

Here you go, programming languages and their salaries:

https://insights.stackoverflow.com/survey/2019#top-paying-te...