Yes, but giving something worthless but expensive is not a real tangible proof of commitment. "Here is something I paid too much for" is less meaningful than "h

Yes, but giving something worthless but expensive is not a real tangible proof of commitment. "Here is something I paid too much for" is less meaningful than "here is something very valuable." Something valuable says if you are bad to her you'll lose out and she will have something to show for the commitment she reciprocated, something expensive that isn't valuable says I'll behave how you want to keep you around. In India they give gold jewelry, that makes a lot of sense. Their cultural reasoning about it is very different (it's a financial investment that ties families together) but the act is better IMO.