I think it's way more complex than what you've outlined.
How did you get a negative yield of -75.45%? You're not losing any of additional investment... are you comparing it to another yield generator?
There are additional benefits to Hive... do you need content created or help with other projects that you could fund with upvotes? Are there things you'd want to build on this decentralized blockchain that could be funded (partially or fully) by the DAO?
Obviously you're aware that other people could also upvote you which may result in potentially more than $13,500 in 90 days.
There's also all the community tokens... so if you were voting other people and they were voting you... you might also receive LEO tokens or POB tokens, etc, which would also (hopefully) increase in value over time.
RE: What keeps me from reinvesting back into HIVE or LEO