I get twinges of that feeling. I feel repulsed at myself after because I strive to be unfazed by material things and hold money in contempt-- I shouldn't want cash, and I shouldn't want material goods.
What's a double-edged sword most of the time is I don't want the thing people are showing off, usually. Like, a fancy car? It takes a lot to get me drooling over one of those. A good PC gaming rig? Mine's good enough. It's double-edged though because usually I start thinking "What would I do if I had that money-- just a fraction of that money, even!" And that's... at least I'm not feeling jealous at the person, yunno? But I'm like... still filled with frustration over what I don't have. I'd like some machines that help with maker stuff, for example. Or to have some money squirreled away to pay off college loans for a few months and keep those off my back. Just a few months of peace. And it's a sense of anguish having that over my head. Even though I strive to be anti-materialist as possible.
Sometimes I feel like "Well hey, at least some of the people on this forum're wealthy. There's opportunity there of some kind." But no real plan forms for a way to actually do anything with that information, yunno? What'm I gonna do, come in and beg cap in hand for cash? If I had something more concrete, then maybe-- and yeah, duh, I'm looking for a fuckin' job most of the time instead of pinning my hopes on nebulous ideas. Don't fucking worry, my plans A, B, C, or D through Z do not involve using ERA to catapult my way to fortune. It's an obviously illogical impulse with no actual concrete actionable basis. It's just as irritating, in some ways, as that twinge of envy or frustration I get. And I can't tell if it's any better or worse than those feelings either. I don't want my relationships with people to be transactional, to be "what can I get out of this person." How's that any less materialist than being jealous of someone's computer rig?
Reflecting on this just deepens my suspicion that money tends to be an inherently dehumanizing thing, for people that have it and people that don't.