Well, people are not wise with money. I think we know that much living in this world.
Actually this engagement ring (or any token for that matter) would sound a lot more persuasive if it was something that you had come up with yourself, something special to you. But since you're just doing what everyone else does, the same old routine, what does it even mean? It means you can afford a ring, that's it.
Of course, in principle, everyone can afford a ring because it's supposed to be like 1 or 2 months worth of wages or something (at least that's what I heard), which means even if you have a very low paying job you can still buy the cheapest one I bet.
It's like buying greeting cards where the message is already written inside. Lazy and without effort.