u must have 300k to do this buy up 50k bronze arrows at varrock arrows shop the most they can be is 6gp (do the math), then sell them for 20gp ea, u make 1mil (math) awsome right?
How silly. For one, people might not have 300k to start out with. For another, buying bronze from the store is not a set flat rate; inflation from the shops come into play here as well.
I'd say the best way to get rich would be to work hard at a skill for 2 weeks, such as Runecrafting or Fishing. Those are pretty decent money makers. Or, you can pick flax and spin that, which makes for a hefty penny (and everyone who does fletching WILL buy flax at some point).
If you have 300k there are better ways to make money than that. You could merchant ess or buy yew logs and make bows and sell/alch. Buying coal and iron and making cannon balls.
Personally, I rc nats in the abyss for my money. It's not too boring and it's quick. Pouches make it a lot faster though too, be sure to use them. People will always need natures.