Thank you, you deserve the full "congrats !!"
I knew people would try anyway, but it is really unfeasible, I removed the last upgrade step (896) in my calculations for the market, but I forgot to reduce the last upgrade, so the overall market sales are 2x896 coins short... And I went crazy with the 200 gold, with no time to test, it takes way too much time to mine, sorry for that !
I agree that it might seem weird that the reward goes down, however it would be less consistent with real sales: You are the seller here, so, the more you sell at once, the less people will pay per unit... And it is also more rewarding at start for the player, when you really need to improve your trolley, and less rewarding at the end, when you are simply farming for the last upgrades...