Interesting question. I did it a little backwards - throughout the 80's and 90's I was spending $100/month on average on vinyl and CD's, yet had a middling Sony receiver and Infinity speakers. Once I found myself more interested in buying music than listening to it, I realized I had a problem. I also looked at my collection and realized it was worth much more than my system, and so started my long audiophile journey.
Over the last 10 years, I've spent much more on equipment than music. Now that I"m finally pretty fully satisfied with my system, I'll spend a bit more on the room, but then plan to go back to buying more music.