A cool but totally non-profitable ability that is completely unprofitable. Smithing is the art of turning bar materials into items. You would be RS gold better off selling the bars than to make something from them. For instance If you plan to create rune plates, you'll need five rune bars, each of which will cost approximately 17k. 17x5 = 85, which means you'll spend 85k making the platebody. Unfortunately, a Rune Platebody will cost about 60k. That's basically saying you've lost 25k. If you don't want to lose money do not forge.
Did you think that forging was all there was to Smithing? Not so! Smelting is another option. Smelting is when you convert ores into bars. The best thing about smelting is that it is very profitable. For smelting steel bars, you'll require 2 iron ore and 2 coal ore. Iron costs 100 coins and coal is 178 coins. For 1 bar, you would need cheap RuneScape gold 1 iron mined and 2 coals. You would also have to sell the ores for around 456 coins. But if you smelted them, you'd have around 163 coins more, because a steel bar weighs 619 coins.