This is exactly my test. I buy a lot of frivolous things, but try to make sure they’re things I really love and am not just buying because it’s on sale/a designer brand/The salesperson is right there/I’m too lazy to mail return it. There’s not a ton of things I have bought that I don’t really love and get excited to wear.
And, FWIW, seconded that the dress seems risky/sacklike/overpriced (but buy it if it brings you joy! -the girl who bought a $70 gold-plated ring a few weeks ago and has worn it every day since because it spoke to my soul).