From what I've seen some whale upvotes are worth more than a hundred bucks (or at least were worth that much a few weeks ago, should be a bit less now...)
But one could argue that this is exactly the reason why the price of Steem and SP is so low - if it was higher it would be more beneficial to upvote yourself and create Steem without contributing to the platform, thus lowering the price back down.
So the fact that upvotes aren't worth that much now might stem from the self-upvote problem