Well aren't you playing devil's advocate here...
1. Prohibition benefits the criminal element. Ladies need a lot more "management" because they need the manager's experience to evade arrest, the requisite expense of a defense, screening for LE, the know-how marketing carefully in the shadows. All of those barriers to entry are due to prohibition.
2. Ending Prohibition ushers in regulation. Regulation breeds more safety. In some jurisdictions, the courts and vice already do STD testing during booking. Regulation should lead to licensure of management. For example, preventing those with criminal histories in violence from legitimating participating. Regulation could also require frequent testing, with stiff penalties for evading such.
3. Taxes! You can tax that which is legal. Tennessee even tries to tax that which is illegal... but that failed pretty miserably. Management is more expensive for being a crime. The market will pay what it will pay - more money is available for the ladies and the public coffers if management is no longer an illegal activity.
4. Trafficking! If being a legitimate, regulated manager/agent is no longer illegal, the traffickers are now more at risk - as there would not*be a fear of arrest and prosecution for legitimate operators exposing the traffickers to law enforcement. ICE could work then work with the community of licensed agents to uncover criminal operations. In addition to the boon to fighting the trafficking issue; "pimps" would not get licensed, due to criminal histories, and the end of the easy money. Then being an unlicensed promoter of prostitution would necessarily have stiffer criminal statutes.
5. Benefit to Johns? No criminal charges, sure. But I don't think the "rates" would be much affected. I don't think there can truly be a comparison with substance prohibition - as the COSTS in moving the product were significant, thus the supply costs necessarily affected the market price.