The fact that crafted items cost 3x the raw materials cost applies only to things made with the craft skill, and craft skills only let you create things where you provide significant 'value add'.
The sub skills of craft that definitely exist are listed at Are there definitive types of Craft (XYZ)?
You will note that none of these craft skills cover melting gold into a mould. Blacksmithing refers only to making things out of Iron, for example. http://www.dictionary.com/browse/blacksmith
The DM may, at his discretion, invent new types of crafting of course.
This means that you can't (DM discretion aside) use the Crafting skill to make gold ingots. Crafting is a skill. Applying heat to gold is not.
Ah-hah, you say! I've got it. Instead of making gold ingots, I'll make golden armour! That way I can use the armoursmithing skill.
Unfortunately, that won't work either. There is a generally accepted principle that buyers and sellers for individual items may not exist, or prices may be impacted by events. The DM sets what items are for sale, and for how much, and decides what prices are offered for items you sell. If there is an iron shortage because kobolds invaded the Nashkel mines, the price of iron items will rise, or they may be unavailable. If certain countries are flooding the market with iron to drive competitors out, the price will drop.
So, you make 10 suits of golden armour, for each one turning 3,333 gold into a suit worth 10k, and head to the village centre to sell it. You pass the cabbage merchant, who is busy haggling with some scrawny farmers over a copper or two. You advertise you wares at market price, only 10k gold for a golden suit of armour! A farmer throws mud in your direction, then turns back to the cabbages.
You head into the capital city, sure you can sell your goods there. You go to the King, and he likes the look of them, he buys one - you're in business! A Duke looks interested, until the King pointedly clears his throat, "I hope you're not trying to outstage me, Duke Gareth - people have been known to lose a head for less". The Duke puts his purse away and backs away from you.
As you leave the palace, a merchant taps you on the shoulder - "look, no-one will buy your golden armour, I'd be happy to take it off your hands, I'll melt it down into ingots and sell it to the mint. But I can only pay you 2,900 gold coins per suit, because I then have the expense of melting it down and shipping it to the mint, who will buy it off me for 3,333 gold. Have we got a deal?"
Total profit = 6666 (profit on the one you sold to the king) - 9* 434 (loss on the ones you had to sell to the merchant) = 2,760 gold, but you can now never do this again. Hardly game breaking. (note, I didn't look up how much a gold suit of armour costs)
By 9th level, when you get access to fabricate, the heroes are so rich relative to the disposable income of a large country that any significant money making scheme will run into issues of "there are no buyers who can afford what you're charging".