There is a bot that automatically votes for your post if you promote it! https://steemit.com/steem/@heimindanger/don-t-use-vote-selling-bots-use-promoted-instead-a-bot-that-upvotes-you-when-you-burn-money
Pretty cool!
Unfortunately, that will probably the only vote you get from promotion because you will be so far down on the promoted tab that it is unlikely that anyone will find you there and upvote you. That is a problem that needs to be fixed. Right now, it is only really worth it if you do $10-$15 or more.