Not really. On steemit there is a price level where a vote does not count for a reward if it is the only vote you got on a particular post or comment.

If you have a post and three very low SP people vote on your post, yet the post payout does not make it past the $0.020 price range, then those three votes go away, and you get no reward, and the three people that voted for you get no reward for curation.

Now if as a participant in @dustsweeper, on day five or day six, it will detect that your post payout is at the dust level (won't receive a payout) @dustsweeper will come and provide a vote to raise it over the dust level so you get a reward, and the three people that voted on your post get a curation reward. @dustsweeper is not an upvote bot, it is a dust level vote rescuer.

The absolute largest vote you will ever get from @dustsweeper would be something like $0.025. All @dustsweeper does is, like I said, rescues low level vote that would have been burned by steemit.

@dustsweeper will not vote on your post that have no votes. It will not vote on any post or comment that has a payout over $0.025. It will vote on any post or comment of yours that has a vote that is below that reward level.

As for how soon after sending in 1 SBD to help lift those dust votes, it happens pretty fast.

I hope that cleared up the difference between an upvote bot, and @dustsweeper. You are not buying anything. If all your post and comments that get voted on always exceed that price level then you will see no results from it, that is highly unlikely to happen.

Also they do have measures in place to prevent people from gaming the system, example a second owners account giving lots of little votes just so their other account can get the dustsweeper vote.

It was designed to assist new users receive rewards from the votes of other new users, instead of those votes and rewards being burned up by steemit.