Teams hiring developers versed in specific languages, libraries, databases, http servers, deployment orchestrators, etc are doing it wrong.
Hire good developers. They will learn whatever technology your company uses and/or built.
Hire good developers. They will learn whatever technology your company uses and/or built.
A better one would be: "Hire good developers. You can invest in teaching them whatever technology your company uses and/or built."
Otherwise you end up with companies that hire good developers who don't know the tech stack and expect them to be 110% productive in one week with no investment from the company in training them. Then, even if the developer can keep up with demands they end up writing sub par code due to unfamiliarity with the tech stack.
That being said, if you have the money, Haskell developers will absolutely follow - and in some domains the project will actually be cheaper.
Besides which, an employee with a fully-loaded cost of $200k/yr can be sent to a one-week external class for well under $15k including salary, tuition, travel, and expenses. That's far less than the cost of acquiring and onboarding that employee; and if you don't care to train your staff, they'll jump ship for an employer that doesn't suck the stars out of the sky.