I've talked to at least one persons who works on production Haskell applications, and Jane Street, a company that was discussed on HN just yesterday makes heavy use of OCaml, but yeah they're pretty rare and I suppose the people working with them are just lucky. I've heard particularly about the Haskell market that if you want a chance of competing for the few jobs available you have to be among the top-haskellers, but I'm not sure.
Jane Street being the only company that anyone ever mentions when discussing OCaml is even worse in my opinion. It means the ecosystem is going to be heavily driven by their needs, not to mention that banks tend to have idiosyncratic development cultures.
It is not the only one though. There are Ahrefs, Tarides, Tezos, Citrix (XenServer and a part of Xen are in OCaml), Inria, Facebook (for compilers, typecheckers and ReasonML), Bloomberg (was Bucklescript/ReScript, now at facebook though I believe).
There are also some academic projects with industrial uses. Directly to mind come Coq, Frama-C, Mirage and the Zélus compiler.
Both INRIA and the CEA uses OCaml heavily (Coq, CompCert, Frama-C). Cambridge uses it for MirageOS, Facebook to write software analysers and now web applications (the web version of Facebook Messenger), Citrix in XenServer. Bloomberg developed a compiler from OCaml to Javascript.
Jane Street only gets mentioned so often because it is one of the highest paying and selective companies in the world. They are not in control of the ecosystem. And they have nothing to do with banks.
