Ben:
Your post underlines the assumption of this thread, but an assumption I don't necessarily agree with -- that bunkers are necessarily expensive to build and to maintain.
In Scotland, they spend a lot of money and crew hours rebuilding those revetted faces, but during the playing season they send one man around the course in the morning, walking, and carrying a rake to take care of them. I guess that costs $30,000 a year more than having no bunkers, or about $1 per round. Are bunkers worth $1 per round?
Also, at least on sandy sites, building bunkers doesn't cost very much at all. It certainly costs less to leave the sand than to irrigate and fertilize and mow the same area, so the only question is how much you are paying to shape all those bunkers. It can certainly be quite expensive to get a contractor to rebuild them on an existing course and try to follow old photos of what they looked like with any measure of accuracy ... the cost might be $5000 or $7500 per bunker in that case. But to create them to begin with is mostly shaping work, and the entire shaping budget for a course might be $300,000, of which maybe a third (and no more than half) would be assigned to bunker creation ... so are bunkers worth an extra $100,000 out of a $2 million or $5 million construction budget?