Comparing the cost of your own wedding to an estimation of the flowers, catering, venue, and bar of the wedding you're currently at is rude and speculating about why a couple is getting married is even more cringe-worthy. If you're not going to a wedding to support and celebrate the couple, then you should probably just stay home. Any conversation that could offend someone (especially the people paying for the wedding, or the couple getting married) should just be saved for a snarky text to a faraway friend if you must, but definitely not for the dinner table.
Sure, we're all well aware that the wedding of a 21-year-old cocktail server marrying a 90-year-old real estate billionaire is probably not out of pure and true love, but if you're invited to the wedding, are you going to bring it up money every five seconds? Probably, but you could at least have the decency to whisper and save the observational comedy routine about sugar daddies for brunch the next day...