shorting of stocks, no calls & puts, etc. Some people were getting $100 and up for their ports, but as the game has grown, with shorting now, funds, etc., the prices on large ports have gone down as more people have bigger ports.
I've seen $1B ports sell on eBay for $10, and sometimes less. Obviously, the larger the port, the more $$ it could probably be sold for.
I'd be REAL curious how much grory's port would sell for, since she is ranked the #1 player lifetime, at $19+ Billion. No one will ever catch her, IMO..she's just too far ahead of everyone.
Hope that gives you a little insight...