I'll occasionally take shots at my sister for this (because, well, she's my sister and she loves taking shots at me too so it's fair). But my God I don't dare challenge the issue of spending extravagantly on rings/weddings with another woman (I once did, it didn't go very nicely for me).
But... overtime here's how I've come to rationalize it: symbolism is a strong emotional asset. If it helps make the girl happy, then it's worth it -- because mental happiness is worth it; because mental health is a component of your overall state. And hey, afterall, I did spend $700 on my chair, $300 on my kinesis keyboard, $800 on my LCD monitor, etc. etc.