Seems like an american things really. In France, nobody would expect anyone to buy a certain kind of ring. As long as it's pretty, you can go for anything. Or no engagement ring. Some friends of mine don't even get wedding rings. And I just met a not married couple wearing rings just because they liked it. Our wedding ceremonies are also usually way cheaper and less show off that the ones your pop culture is selling…
At least in the nordics, I don't think there's a specific type of wedding (EDIT: or engagement) ring that you're expected to have, and I think many people have no stone of any kind embedded in theirs.