Upvote buyers get 120% of their bid in upvote and if they send more they get the changes back. But not all of the upvote is paid to authors. About 20% is paid to the curators I believe. As with delegators, whatever liquid revenue is made is split between delegators everyday. The extra ROI for delegators will be paid in SwiftCash funded by curation rewards. That won't happen until @swiftcash SP reaches 1300 first.

But right now I'm the only one buying upvotes :(
So I would advise you not to delegate unless you plan to buy upvotes. We really only need to sell 10x 100% upvotes everyday to make the best of the delegations. Right now, if you look, it's just me buying upvotes for random posts to promote the bot...