If you start a company and spend a non-trivial amount of your time, effort and money into handcrafting and customizing a perfect IRC server, that company is going nowhere.
If you know IRC well enough to want to mandate it for your company, you can probably set the server up in an hour or three. You can then install https://thelounge.chat/ and have your employees log into that for browser and mobile apps vs. native IRC clients.
What money would it require? Any leftover PC from the last 15 years can run the server.
Aggressive delegation to third parties is how we end up with all these complex services. A chat system, a ticket service, a git interface, should be pretty trivial to install and maintain. And consistent too.
What money would it require? Any leftover PC from the last 15 years can run the server.