I live in a town of 15,000 and I sell about 1 pro3 a month on top of pro and pro plus. It has nothing to do with how many people in a city. The detailer in your community has the responsibility to market his services. That will determine how many installs he sells. Pro3 just like all opti coat coatings need 12 hours to cure before getting rained on, etc. Pro3 is no more of an undertaking than pro+. On a side note, pro+ is capable of lasting the life of your factory clear Coat without regret that you so not have 3 installed.
Fun fact, I don't know why detailers don't advertise instead of trying to sell different coating brands. You won't hook people based on the brand. If they would just offer a solution to a problem they would eventually see a steady sale and increase in coatings. 😁