How to I make a Develper Product give a given amount of "Money"?

I've been trying to figure out how to make a Developer Product give a given amount f "money".

You'd need to work with leaderstats or a custom system.

In your script, once the purchase is verified (simple MarketPlaceService), you would have to update the leaderstats (or, again, custom system) with something along the lines of... leaderstatsvalue = leaderstatsvalue + 1

Hopefully you're not too confused. Here's a wiki article on leaderstats- Leaderstats