I have a hard time controlling prices with 500m but i'm easily pumping 10m a day out of multiple items. Jagex has made manipulating a lot harder, and I doubt you even know how to use ge.
I would Rwt in the party room, multilogging. I wouldn't really do much, playing alone would be boring as hell. I guess going to a place that's usually crowded, and doing stuff by myself.
Okay, i'd logoff and take a pic of: World 1: 0 players, World 2: 0 players, then laugh at everyone saying MEWHAHAHAHAH me took that pic!
No really.. i'd either RWT (not much since my rich acc just got banned xD) i'd go Green Drags and enjoy all my dragons... or go Bandits, or yaks... or i'd steal cookies, when noone can see me, why not?