Metal collecting
Metals are a collectible in The Sims 3 and are found in ore form, to be smelted into ingots for §40.
Sometimes the foundry will return an ore, saying that it is actually a Mysterious Mr. Gnome in disguise.
Smelted ingots are worth 175% of their original cost, and so the raw metal must be worth §54 to offset the §40 cost of smelting and break even.
The "Breaking Even" equation is as follows: §54 (Cost of Ingot) * 1.75 (Smelting Worth Modifier) - §54 (Cost of Ingot) - §40 (Cost of Smelting) = §0.5; thus this is the lowest whole number that does not lose money.
Many, many editors have contended that §23 is "breaking even". Plugging into the correct equation, §23 * 1.75 - §23 - §40 = -§22.75, and thus is losing money. If you were to sell the raw ore, you would have made §23 and paid nothing, for a profit of §23, whereas if you mail it to the smelter, you will have paid §40 and made §40.25, for a profit of §0.25. It is far more worthwhile to sell a raw ore up to §54, at which point it becomes worthwhile to smelt it.
Also take into account if your Sim has the "Metal Collector" challenge there is a possibility that smelting will lead to additional ingots you would've missed out on if you had sold the raw metal. Not to mention there is always a chance of getting a Mysterious Mr. Gnome which is worth $1000.