Compare this to pg's essay "Stuff": http://paulgraham.com/stuff.html : I have too much stuff. Most people in America do. In fact, the poorer people are, the more stuff they seem to have. Hardly anyone is so poor that they can't afford a front yard full of old cars.
PG should look at a city sometime. People with junk cars can't afford to ditch them, not can afford to have more cars than rick people.
Actually, what happens is that poor people are afraid to discard their unneeded stuff, because its modicum value is still value. Whereas in the middle class, at the end of the day, 90% of the stuff you have can be thrown away because you can be mostly confident that you can buy it again if you find out you needed it after all.
Most of what us non-poor people can't throw away is either sentimental, rare, or a major investment (a pool in your backyard, for instance) that can't be easily recouped.
In short, if you feel that you have a choice in the matter, that's what wealth is.