And this is going to get worse, as we see paper progress reports decline in importance and frequency. I expect that we'll see future Worldcons make "electronic copies of pre-con publications" the default, and that eventually the traditional progress report will disappear entirely. As you know, that will reduce the marginal cost of a supporting membership even more.

I would expect a $20 "voting only" membership to be attractive to Worldcons, as I figure it would cost less than $2 in direct costs to service -- even less if set up in such a way as to not requiring paper mail of any sort -- making it very profitable in percentage terms.