Disclaimer: Not every woman wants an expensive engagement ring. This post is for women who do.
In the U.S., many women seem conflicted about how much money their prospective fiances should spend on engagement rings. There seems to be no definitive answer, though the 2-3 months' salary standard is mentioned frequently. This means, for example, that if he takes home $100k/year, the ring should cost between $17k and $25k.
Many people think this seems outrageously pricey, but I disagree. You should not feel ashamed for wanting an expensive engagement ring, if it's important for you.
Here's an anecdote:
In the late 90s, I was a serious pianist and had my eye on a $40k piano. I explained this to my dad, and over the next two years, he scraped together $40k and bought me the piano. My dad earned less than 6 figures at the time and worked hard for his money. Today, I consider the piano a family heirloom and feel grateful to my dad for doing the best he could.
The lesson I extrapolated from this experience: if you date a man seriously and give him your best effort (your youth, time, energy, etc.), then he should feel the desire to give you his best effort.
Hopefully, my story illustrates what a man's best effort can look like. If a middle-class man can save $40k in 2 years to buy his daughter something she deems important, then the middle-class man you're dating can save $40k in 2 years to buy you the engagement ring you want.
My current bf set me straight about how garbage my ex husband's proposal was. It made me feel terrible at first (it was a family heirloom but a family heirloom in MY family, he didn't invest or make an effort at all) but now I see he is the one who had to help me see my own value. He's also made comments about men's poor taste and no fucks given attitude and women's lack of standards when mutual friends have gotten engaged. I'm curious how my "I'd actually prefer not to go ring shopping, you have wonderful taste and know me, have fun" direction will go :)