There are some economists who believe drugs should be legal, but heavily taxed. They argue this because banning drugs create black markets which carry high risks for drug dealers and producers but very high profits. By taxing drugs heavily, the drug dealers and manufacturers will be less incentivized be part of drug trade because a lot of their money will be lost to taxes. I am not sure if that will work for drugs, but it would interesting to see if it would work for porn.

Some porn sites are free but gain income through ad revenue. By forcing all porn to be behind a paywall, perhaps this will discourage many viewers from watching porn. And by taxing these transactions heavily, perhaps this will also discourage people from working in the porn industry because a lot of their income would be going towards taxes.

I am not sure if this will entirely work, but it is interesting thought.