Last I checked about a week ago, the short interest on KBIO was in the realm of 400%. So you'd be paying an interest rate of 400% per year just to be short (that's before any other profit/loss from the trade itself). My guess is that 50% of that is going to Shkreli and/or his "associates", since it's possible for larger players to work out a custom deal with their clearing firm for a cut of the securities lending revenue. All of this just goes to show how absurdly broken and antiquated the US shorting system really is. The existing equities clearance system needs either serious reforms, or to be completely scrapped in favor of something like the blockchain technologies various "fintech" startups are working on.