I used to think that I wasn't prone to envy because I could admire the way that my friends who were materially better off spent their money. I couldn't begrudge them nicer clothes or furniture or houses because those were just the sorts of things I would buy if I could afford to. It was nice that somebody had fine things, even if it wasn't me.
Envy is a bit more insidious than that, I find now. I was content as long as people I knew bought things that I considered worthwhile, but now I find myself grinding my teeth whenever someone I know drops what I consider a lot of money on something I consider foolish, or downright stupid. This is silly, I know -- my friends aren't obligated to conform to my tastes in their spending habits, and variety is the spice of life, and all. Still, it irks me more than it should to think, "Geez, if I had that kind of disposable income, you can bet I wouldn't spend it on A, B, or C!"
Of course, this works both ways. I recall coming back from a sale once with a blazer and showing to an acquaintance. She took one look at the price tag and exclaimed, "Tell me you didn't pay that much for that!" It pleases me to think that I have good taste and an eye for quality, so her response rankled. But then, everyone I know thinks that they are as frugal as they possibly can be, in accordance with their priorities -- they're just not MY priorities.
Which only goes to prove that I'm far more materialistic than I'd like to admit, and that the temptation to envy is stronger than I once thought it was.