I do think they should be paid what they're worth... and if they're the only person in the whole company that can fix the code they wrote in a language nobody e

I do think they should be paid what they're worth... and if they're the only person in the whole company that can fix the code they wrote in a language nobody else knows, then they're indispensable and can charge any salary they want. which is why they shouldn't be allowed to artificially make themselves indispensable without bringing any additional benefit to the business