Conclusion: The car is back on the road. I had the rear axle beam replaced with a good one from a salvage yard for $1,200.
South Main Auto guy, in up-state New York, was replacing a rear suspension beam (domestic car), just contacted a Florida wrecking yard. He was pretty near ecstatic when the replacement part arrived, looked like new compared to the corroded crap he deals with locally. Would be interesting, if someone could quantify how much road salt costs the auto industry.
Eric O had stated vehicles in his area usually fail inspections in ten years without rustproofing. Like everywhere there are shady inspectors to get people by. He has an old Tundra preserved with frequent application of Fluid Film.
This is why I don't think Toyota's paint thickness is a problem. I am a lifetime west-coaster and lived most of my life in the rainy, moist, humid Willamette Valley. When I visited Minnesota a few years ago, the first time I had ever visited the midwest, I was shocked to see vehicles as new as 5 years old with rust perforations in the middle of body panels. No sign of physical damage, just rust eating right through the paint. I've owned cars with as much as 380,000 miles without a hint of rust problems. Rustproofing isn't a thing here either. Even the vehicles with the "thinnest" paint such as Mazdas and Toyotas don't have problems. The answer to your question is, it doesn't cost the auto industry anything - if anything it provides a huge amount of business for them.