So I was setting up my sims stall at the festival grounds and when I went to "buy" to see them, one can of my Lemon Marmalade was 100$!?! Is there a way to make the pricing go down? All I see is markup, and I wanted to make my sim work hard at gardening. So canned goods would go for about 20-50$

There should be an option in the settings Produce-Stand-Interactions#Set-Price-Multiplier

to decrease the price put a minus befor the number.