Just checked and you make a loss of $25 when you mine silver with an iron pickaxe.
Iron pickaxe: $200 gralats
Amount of silver you can mine with 1 iron pickaxe: 25
Silver sells for: $7 gralats each
25x7=$175 gralats gain from each $200 you spend.

I'm pretty sure it's supposed to have some sort of profit to it except from just exp?

Edit: Mining coal also results in money loss