Building banking apps? Well, even if it's Haskell, the Haskellers were dreaming of GPU compiler jobs, not banking front ends. So you're probably down to literally 5 qualified people on earth who want your job.

But then 3 of those 5 don't want to relocate or have other operational desires that require you to re-think how you run your team, and 2 of those 5 believe so strongly in supply-demand that their salary should be 3x the industry average.

Many companies, including Jane Street, come to the same conclusion: If you really want developers of a niche language, you have to be very good at finding smart people who don't know the language and training them.