Racked my brain, which actually did manage to stretch on demand. And remembered that I had been in line after BayCon 2005 for a 2006 membership, but the line was long, and after half an hour of not making much progress towards the cashier, I thought what a dull con it had been, no GOHs I was interested in, mostly dull panels (except for the costuming ones), filk concerts were mostly boring rehashes of the same people and groups doing the same numbers, or not doing filk at all but abusing the concerts to plug their latest non-filk CD. I also did not get to spend much time with people I only get to see at con, and except for farmount's party there wasn't much going on of interest in that area. And I was not sure if I would even be in the Bay Area in a year, what with job foo and plans for Thailand in November.
So I ditched the line, and never bought a 2006 membership.
I was set on not going to BayCon 2006 until I saw an announcement that Pournelle and Niven were the GOHs. That's a WorldCon class lineup, and I was definitely going if I could.
But there was still job foo, Thailand plans (and when I returned I was jazzed about the idea that I might be moving there permanently), and Mom's heart surgery (which kept getting put off until it was finally scheduled for two days before the Con).
Bottom line: I did owe them the full fare, after all.