Another good example to add to your list is Paris Hilton. If you go by your classist definitions, she'd be a Shiraz sipper. In reality, though, the globe goes all the way around and begins again. Most "sippers" are useless dependants just like any welfare leech. They just get their checks from different places. We don't respect them, they are just a different flavor of Jerry Springer freak. You can't class them the same as you class, say, a hard-working industrialist millionaire. Sociologically they will behave, AND BE PERCEIVED, in totally different ways.
If I had any advice, it would be to stop looking at things with these cemented classes. Pull out all the little divisions you have in your philosophy, mix everyone up, and let them settle where they may. I think you'll be surprised to find the pool offers you different striations based on different issues. Factor in, say, waste, or charitable contribution, moral imposition, etc., you might find the lines marking the classes shift.
While the numbers may stay the same, the people do not. Most of what one would consider poor, are people just starting out in their careers. Due to high debt burdens and low income, they are poor. But they quickly move out of the poor (to be replaced by more new workers) and into the middle income group.
The analogy of the numbers is akin to saying since the unemployment rate stays about he same most of the time, the same people must be the ones that are always unemployed. And that is clearly not the case for anyone bothering to look into the numbers instead of at them.