You don't really. The only way to really make money on it is jumping on a desirable item like castle walls were and gathering materials for it before they jump in price and trying to sell a few on market board before people start undercutting each other.
But on the other hand you could be pouncing on something like the odder otter house and it turns out not so popular

submarines is kind of same deal. The cost of making a sub that can semi-reliably get whatever the latest and greatest exploration item is will be so exorbitant that you'll be in the negative for a very long time and just have to hope you make enough
Maybe if you sent out four tier 4 subs for the moai minion, candle wax, and decorative crystal constantly...
but even then your probably going to be down a few hundred million hoping for 1-2M payoffs a couple times a week