The tax collectors didn’t actually work for the Roman government. What happened instead was that Rome imposed taxes on the provinces and then auctioned off the right to collect those taxes. Rome got paid up front, and the investor was reimbursed and earned a profit by collecting the taxes established by Rome. He would typically hire several assistants to help enforce the taxes. The problem, however, is that this system tends to turn a blind eye to corruption, as nobody in power cares if the tax collectors inflate the duties and pocket the difference. The price the right to collect taxes got at auction reflected what Rome actually expected the assessed taxes to be, but tax collectors didn’t merely speculate that they could lawfully collect more than Rome planned, but often imposed extra charges on the people, enriching themselves by extortion.