Do you disagree that C# has similarities to other languages? C# is based on Java, which is somewhat based on C++. Basically anyone who does a CS course learns one of these. In comparison, I don't know any programs that use Haskell, oCaml, scala, or ML (I had a single class in which I had to use ML fora single project). What I mean to say is, functional programming is not widely taught. I don't think this is controversial.

Do you disagree that any person that is reasonably smart and that you'd want to hire could become productive in c# within a few days, given that they've used java or C++ before. This is a super-low risk gamble. I don't think this is controversial.

The only indicator that someone can become productive in F# is that they have experience in one of F#, Lisp, ML, Haskell, etc. I don't think this is controversial.

Hiring people is hard. Maybe you haven't been involved in the process, but you have to interview hundreds of people just to find that one person who is smart, is a culture fit in your company, and has enough self-discipline and a high-enough level of consciousness to go about their work in a pragmatic and intelligent manner.

Now imagine that you are CTO of a new company and you are deciding between c# and f#. If you startup becomes successful, you'll have to quickly ramp up in hiring engineers. If your startup doesn't become successful, you'll quickly have to ramp up in having someone else hire you.

Assuming we are a rational person, that is we are doing a startup in the hopes that it will be successful, then our plans will facilitate the hiring of many engineers.

Fast forward to when we need to hire many engineers. Also, remember you don't have loads of time to spend doing this, because you're the CTO of a startup and you have shit to do. Also, remember it's hard for startups to hire because 1) risk and 2) you aren't google.

Now imagine taking your pool of candidates and reducing it by 99%.