I know that everybody (including some of America's Most Influential Rabbis) disagrees, but personally, I think that kid's Bar Mitzvah party is nobody's business. Did it cost more than I will ever make in a year? Yes. Did it have anything to do with what I think of as important Jewish values? No. Would I have enjoyed being there? God, no. And my conclusion? So. And also, What?
Let's face it: Lots of Bar and Bat Mitzvah parties have nothing to do with Jewish, religious, or ethical values. Lots of them are vulgar. In lots of them, people - particularly women - are dressed well beyond the bounds of traditional Jewish definitions of modesty (though many of those are family and guests). And my guess is that many of those took a greater proportional chunk out of the families' discretionary income than this one did. We don't hear about those, though - probably because those don't have quite the volume (read: they didn't cost as much) as this one had.
Also, there are probably lots of Bar/Bat Mitzvah celebrations that cost a whole lot more than this one did, but we don't here of them, either, because they were in Better - or at least quieter - taste. A celebrity performer? A luxury trip abroad? Why not? As long as it's not tacky.
Be honest: the values at stake here are not moral or religious but aesthetic. And if you've been elected Censor by the Centuriate Assembly, judging the aesthetics of a private family function is precisely at your pay grade. But otherwise, unless someone is trying to force you to adopt that kind of taste as your own, why is it a subject for your public judgment?
Look, you want to use your pulpit to inveigh against the kind of wealth inequality that allows one family to spend on one event what most other families will never make in a year? I'm right behind you. You want to establish sumptuary rules so that all simchas are affordable. Rock on (but good luck with your congregants). You want to insist that all Bar/Bat Mitzvah kids and their families demonstrate a commitment to a life of piety and good deeds? Yes, please.
But if you don't object to private fortunes, if you don't insist on a common standard of taste, or an overarching expression of piety in family celebrations, then maybe a better, more pastoral response would be to stand in front of the prurient crowd, and protect a family from a public shaming. Isn't that a Jewish value, too?