No I do not underestimate profit incentives. I just realize that these things are not always so nefarious and there’s plenty of money for people to make by bringing things to market.
Regardless - cost effective, portable desal devices will be dramatically more profitable than sitting on a patent for 20 years (if even enforced!). Most people buying imported bottled water due so because they are lazy not because they are without access to potable water.
Your overall point is fair, but your math here is off by a factor of 1000 - it would be around 380 GB.