If someone makes $250,000+ a year, it's not unreasonable.
"My 2005 Ford Focus sedan was $3,000 and should last me about 3 years before I need to make a decision about major repairs, so that's less than $100 a month in ammortized costs."
That's completely unrealistic. You have some sort of competitive advantage (REALLY know someone trustworthy), or you are delusional. $3000 cars are generally very high mileage, unreliable, in poor condition, etc. Timing belts, suspension components, drive belts, starters, ac compressors, minor electronics, etc tend to start going on these cars.
"Are there really hundreds of thousands of people who are making $5,000+ a month necessary to justify the purchase of such an expensive vehicle? I'm not far from that number and most of my money still goes to food and rent."
I believe a car should be 3 months income at most. So no, I can't justify anything past a $10,000 car.
What I can say for sure is that unless you are a decent mechanic with tools or have GOOD friends / relatives that are, you shouldn't walk around espousing 3k cars. They just cost way too much in time.