it ain't normal to want to see the man you are supposed to love unconditionally, to financially bleed on impractical trinket that some people pay with almost proper enslavement, so you can brag about it with your friends (you = anybody, nothing personal here).
if that's an US norm, so what, it's still wrong on many levels. it ain't like that here in europe. the last ex-gf that mentioned 3-salary rule for it was exactly the type you should never, ever marry, no matter what person you are. my fiancee on the other hand is happy with 70 euro ring since relationship is about everything else, but this.
if woman sets this as non-negotiable standard to get married, there is no love from her in relationship, just pure calculation and she treats her counterpart like an idiot. simple as that.
If she wants a diamond so badly, she can spend her own money on it.
If I really want a sports car, I don't expect my fiance to buy it for me. If I want a cellphone, I don't expect my girlfriend to buy it for me and pay for the service.
Or may be, just may be, wanting diamond is just normal for some women, and it doesn't indicate whether she is a good couple or not.