I don’t want to make this long but want to make it straightforward; I think the shop prices should be balances based on what the material is.
Not sure on what the price is for every item so keep that in mind, but I do find it confusing that Iron Armour is 10 Gold, and an Iron Sword is 5 Diamonds. They’re the same material, so it would make sense to have both of the materials either use diamond or gold.