The quality of the posts that gets submitted is a huge factor. Once the upvote bot gives an article more visibility, the users will then start upvoting it and making it profitable. A lot of the upvote bots will give a larger author reward than what it costs for the service let alone all of new users that the high vote attracts. Let the users posting garbage content waste their money on the upvote services. It's more money getting poured into the system overall.