If you become our member you receive one vote a day from Qurator. The value depands on the Tier you are on. Qustodian is an addition pay for upvote bot for members that would like some extra boost. You do not have to use it.
The money on the post do fluctuate with the price of Steem. That is ow it works for everyone here. Right now Steem goes up for example and the votes on everyones posts are bigger.