Paying a dev to code a custom gamemode

Hello! I have recently thinking about how to improve my server, and I was thinking of making a custom gamemode. This idea for a gamemode is so evolutionary, I can't even share it on PMC, but to the point of the post.

I am wondering how much money it would be if i wanted to pay a developer to code me a custom gamemode. This gamemode has multiple GUI's, and I'm sure it would have a bunch of bugs, so I'd also need the dev to continuously update the plugin, adding features and such.

P.S:
I'm not looking for devs in this post, just looking for someone who has experience with big dev projects, to tell me a ball park price.