"I guess I have to..."

I use the same guideline, but I use it as such, and not as a rule, to keep myself in check that I'm not overspending carelessly. If something is below that threshold I don't have to worry too much about the purchase; if it's over that, I have to know it's something particularly special (2006 3F Doesjel, for example). Then, once I've made the purchase and instead of being a piece of merchandise, it's beer that I own, I don't think about the price at all when drinking it. I've done that once or twice and every time I have the only thing I could think about was "was this worth $x?" instead of "was this a good beer", it was no fun.