Let me indulge a bit of bio here. In 1999, when my son was a newborn, I opened my own firm and did not take any vacation for 4 years. During that time of ultra-work my business got firmly situated, and money started flowing quite nicely. After 4 years of no trips, we splurged in 2003 and went to the Polynesian for 9 days. Given the "package" that we bought through our travel agent, we really didn't know how much the room was costing versus everything else, and just assumed that the thousands we shelled out was the cost of a really cool trip. Back then, the website was harder to explore regarding options, such as deluxe versus moderate, park hopper versus park hopper plus. In short, we were willing to pay because, hey, we hadn't been anywhere fun in 4 years, and staying at the Poly wasn't that much more expensive, I think, sort of, "Let's just book and be done with it."
Then we became addicted to the convenience, the niceties, etc . . . especially at the Epcot resorts. For us, it's now mostly about convenience. We thus minimize the time we wait for buses. We now own 300 points at the Boardwalk through DVC, and that's where we stay, in a one bedroom villa now that the family has grown.
As to the millionaire thing, well, yeah. Being a millionaire isn't as unusual as you may think. Many teachers, for example, if you were to slap a present value calculation on their pension plans, would fit the definition. In hanging out in the lobbies, I believe many people who stay deluxe are indeed millionaires and/or some parent or other relative with big bucks is picking up the tab. In general, however, I assume most of the deluxe guests are either millionaires or have a six figure income, or both.
Finally, many people splurge with the credit card, and create huge balances without much thought as to how it's going to get paid off. Somehow, those people stand out.