The historical purpose of an engagement ring/gift was to demonstrate your serious interest and your intentions. Via spending money for her that cannot be taken

The historical purpose of an engagement ring/gift was to demonstrate your serious interest and your intentions. Via spending money for her that cannot be taken back. Unfortunatelly, diamonds fit this quite nicely. Actually, the best way to demonstrate it is via these rules: (1) you have to get something that is very hard to get (more money than you normally have), (2) something that has no use for you (you want to convince her, it wouldn't be convincing if you benefitted from spending) (3) and preferrably it is not monetizable for recipient (in general, woman is much less motivated to tricking you only because of gift) So, if she's already convinced to merry you, spending fortune for diamond ring is futile. And if you are in hurry, you can really just burn some money to ash in front of her, it would do the same :) Nonetheless, not as fancy as diamond ring for her :D