[zeusk]

For me, it was an introduction to basic finance topics like abitrage and trading; also the enormous scope of scams people can pull.

I made my fortune in high frequency trading of rune sets after they introduced Grand Exchange and steel smelting prior to it.

[shiado]

I was one of those assholes that ran a bot farm to devalue your labour. RS was a great place to learn about the race to the bottom, economies of scale, and other random economic topics as well.

[omegaham]

The most interesting part of RS was that the more raw the product, the more it was worth - you could get more XP out of it.

And before the Grand Exchange, buying in bulk cost more than buying small amounts, because buying large amounts of materials required you to sit on World 1 spamming "buying iron ore whatever each" for hours.