Great points! Sorry for any confusion. So with my current personal script, I just went in and assessed and assigned prices to everything. When I generate the shop, I take that price, add anything relevant (like armor or weapons price because i had base types for things like +1 armor), and then assign it a random value between 0.75 * base to 1.25 * base.

I agree, the prices would still be very arbitrary and based solely on my opinions. I would like to explore options on getting feedback or even allowing individual "overrides", but that would require like user accounts and stuff that I don't want to manage and most people don't want to make.

I hoped to help that with a sliding scale that would be a UI slider, so you could scale it to your world's magic item prices. So say in your world a potion of healing is 5 gold, or maybe its 500 gold. The slider would scale all the prices. Like for instance, base price of a potion of Healing is 50 gp. So if you put it down to 10 gp, everything is reduced down to 20% base price.