How to make it so that when the player sells something it wouldn't be unfair?

You probably see the title very confusing. Well, my issue isn't about scripting or debugging my scripts. My issue is not hard to solve but I find it very hard to do. Well, you see I'm implementing a selling system in my game but I'd rather call it "publish system" because my game is a simulator game of writing. Yes, you guessed it. The title of my game. It's "Writing Simulator". I made a currency called "Gems", you obtain it by publishing your notes more frequently and upgrade your tool when you can. So to write or make notes you must use your starter tool called "Single Sheet Paper" you can write on that until your spaces to write ran out. So you probably think "Where's the problem there?" well, here is the problem. When you publish it will multiply the multiplier of the tool to the quality of the tool and it will add the value of how many have been written to the answer, and the answer is added to the value of the coins (Another currency that I made). So now the process of converting the number of notes written to coins is done, now let's proceed to convert some amount of notes to gems. Well, that's where the problem comes in. I don't know how to make it fair. When I multiplied the multiplier to the quality and divided the answer to the number of notes written then the answer will be unfair because if they just wrote 1 notes then they will get TONS of gems! But if I subtracted the multiplier to the quality and added the number of notes they had written then they will get gems but the same amount of notes written, that's also unfair because I've said to obtain gems you must publish more frequently and upgrade your tool when you can. Please make me another solution for converting the number of notes written to gems. Also, the multiplier is always 1 step higher than the quality of the tool.