It doesn't help a bit that you have to buy your kids' way up the class ladder. Well, buy them the opportunity, anyway—not living it at home, they may still not socialize to the "right" tier. Housing's more $/sqft in good school districts, or even more money for prep school if you're quite serious. Activities and sports, more money, especially if they're the "improving" sort where they'll mingle with your social betters. The sky's not the limit on that stuff, but for people working for a living it may as well be, since the ceiling's "summering" in the right places, sailing lessons, shit like that. Down the line those turn into better higher ed opportunities, better (richer, anyway) friends, et c.

You can absolutely resist spending extra on kids that way, but there's always that pang of guilt that they're missing something that might've made their lives a whole lot easier down the road (due to granfalloon-sort stuff, mostly, or knowing the right people). Might they marry into money if you send them to that summer camp? If you send them to a school where it's assumed everyone's doing serious preparation for the SAT and for college applications, might that not bump the school they get into up a notch or two on the name-recognition scale? Most spend at least some on this if they can—a couple moderately-priced activities per year and housing somewhere you wouldn't live if not for the schools, say.

It's all probabilities and chances, but the more you spend the better the worst likely outcome gets, too, and the bottom on that can be quite low indeed—it's not just dirty-ol' middle class envy. It's hard to resist.