Although this is a funny thread, the issue can be really serious, so I'm going to give a real answer. Can you get away without buying a piece of crap? Probably, but you need to figure out why everyone doesn't agree with you that engagement rings are crap. It's not just marketing that's at stake here. It's symbolism. If you're highly analytical, this can be tough (yeah, engineers, I'm talking to you -- and I'm an INTJ married to an engineer). An engagement ring is not just a piece of metal to everyone, and a diamond isn't just a rock to everyone. And those people are not inferior people who lack intelligence, at least not necessarily.
And before you dismiss me as a diamond digger ( check out the ethical crisis -- no way would I buy anything other an an antique diamond), I have a family ring from a cousin of mine. I didn't need my now-husband to buy a diamond and would have chosen something simpler than the ring I ended up with, which was not in fact designed to be an engagement ring, though it is a is a diamond ring. My guy got lucky and didn't even have to resize it.
This works for both of us, but I think it's important to be aware of your own preconceptions and have a thoughtful conversation (or two) on the symbolism of these rings. If both of you think engagement rings are pointless, don't care about diamonds, or decide to avoid wedding rings too, you're good. Skip it. This personal choice really shouldn't matter to anyone else. But what if you don't have the same ideas? People have really different ideas, and as what we're talking about here is a partnership, I think one of the most important things to consider is what the two of you really think and how you feel about your options. Why does person x tree things that way? Listen to each other.
I also suspect that this symbolism can be far more important to women than men, although that's not always the case. Still, I recommend that if you're a man considering engagement with a woman, take extra care to be considerate. Even though I didn't want my guy to shell out lots of cash, if he had been aggressive with low-$ ideas, I might have been annoyed. I mean, this guy wants a dog! Know how mush that costs? And the ring will last longer ;). An engagement ring is an accessory to be worn almost all the time. Even some pretty expensive jewelry can be a good value considered in that light.
Context is important too. I've seen some unreasonable excuses (by non-mustachian types as far as i cn tell). It's only reasonable to say you can't afford a ring if you also can't afford your own expensive things of choice. For exmple, if few months of staying away from Best Buy will give you 5,000$...you know what you need to do.
Sorry for this really long answer. Maybe I should have looked for a different thread, but this is the one that caught my attention.
