I can only speak from my own experience about the
game we're making, but it's a lot. I'm the writer on our team, there's a lead artist, and a scripter. We're all working together and have joint custody over the project, so we're not
technically getting paid (our
Patreon money goes toward commissioning another, secondary artist), but when you factor in the opportunity costs of our labor it gets into the tens of thousands of dollars (especially for our artist).
Now you can easily get way cheaper production costs, especially if you live in less developed country where the cost of living is lower (or you hire people from such countries to work on your game), but unless you can do art/coding/writing on your own it's still going to cost you. For example, a good artist can charge as much as $500 per full-res colored image with a background and multiple characters. Say you need a set of 5 CGs, the price adds up
very quickly. Sure you can go cheaper, but in the end you get what you pay for.