Not sure where you live, but that social pressure was/is very soft in Europe. Absolutely nothing happens if there is no diamond, its just people self-pressing themselves in some variant of childhood-like mentality and competitiveness. In my family line, nobody ever bought anything like that.

For any man, for past few decades (at least 3-4) a woman insisting at all costs on big shiny natural diamond is a massive red flag for undesirable personality traits. Given stable divorce rates and general misery on all sides before and after that red flags are and should be considered very intensively. Once physical attraction wanes, only personalities remain.

I am constantly wondering if we're just the outliers here in my German city (I don't think I know anyone who has ever mentioned a diamond ring in my presence, no matter which generation) or if it's just an American thing. Also I couldn't tell you if we're talking 1,000 USD or 20,000 USD :P