The ecosystem was incredible and it was basically a crash course in Anarcho-capitalism, I'm pretty immune to any kind of scam because of having been in that environment.
I made close to 20 grand as a 16 year old through some bug abuse, over the course of 2 weeks if I recall. But alas, I blew it pretty quickly because easy come, easy go.
E.g., two players put one million gold pieces in their inventory, equip no equipment (so no attack bonuses), every hit on each other is now an RNG roll with identical odds for each player. Battle to the death and voila.
That one's quite basic but there were more elaborate games such as flower poker. The game had a flower seeds item which when planted would spawn a flower on the floor. The flower would be of a random color (e.g. red, blue, white, ...). People would bet on which color flower would pop up, or plant plant five flowers sequentially and try and get something akin to a poker hand (e.g. three of a kind, full house).
Quite silly, in retrospect, as I'm typing this out.
Then of course there was the rampant gambling. The founders of online casino Stake and streaming platform Kick both started their “careers” in RuneScape gambling. IIRC they invented “staking” which was a method of gambling gold against other players, before they were banned. But the gambling economy in RuneScape used to IRL mint millionaires for sure.