Exactly this. The problem with every diamond critique I see is that their very first argument against diamonds is that they're expensive when that is, in fact, the entire point.

Likewise, all the people who cry foul about the De Beers conspiracy are neglecting the fact that this does absolutely nothing to reduce their signal value. If I spend a large sum of money on something which I know to be worthless just to start my engagement, that's an even better commitment than spending a large sum of money on something which I think is worthless.

People who are anti-diamond should really focus on coming up with alternative signals which has better social outcomes. I would personally prefer some sort of trust, where if the engagement is successful the money is donated to our preferred charity—but if it's not, it's donated to a politician I despise.

If we're dead-set on continuing to use pretty rocks as signals, someone should establish a monopoly on a gem which is impossible to procure from exploiting conflicts. They should still make it extremely expensive, but have all the mining be ethical.