The idea was to have the price for each upgrade go up and change to make the game a bit harder but I ran out of time to add it so the levels/cost are all the same.
You're 100% right about the auto mowers it was meant to have 5 mowers that would go around cutting grass instead of passively earning money after 200 seconds. But it ended up having an awful passive income
After the Jam I'm planning on remaking the game from the ground up, with a better upgrade system, levels, shop, and a better overall game.