the only fee that actually goes to me is a 10% profit cut from investors
Paid in silver, I presume?
Yup!
Edit:
Will there be an exchange built in to the game site?
Yeah, there's already a half-assed one. It's pretty crappy as it doesn't have a matching engine (you either need to explicitly hit someones trade, or create one of your own). And to keep it simple, all order are "all or none". Improving it is something I eventually want to do, but something simple (along with a #trade channel) is probably good enough for quite a while