Difficulty: Medium
Money Needed: 1,500,000gp or more.

A good way to make high profits is Steel bars Merchanting. First go to World 1 or 3 Falador East bank and start buying steel bars for 550 each.

You will get small amounts of steel bars, but in no time you will have 1,000 to 3,000 steel bars.

Now wait until the "rush hour" (Mostly around 3:30 - 5:00 GMT) and go sell your bars for 600 - 650 each. You will make a profit of at least 50,000 to even 300,000! Sometimes, higher leveled buy for 650 each. But it doesn't happen everyday.