A few years back I put up our sites for sale (I was going through a burnout phase for a while) - and came up with a price based on one year's revenue and also added a significant amount because of the exclusive (original) content and the unique quality of everything.

I wasn't including copyrights to all the images in the selling price - simply an unlimited licensing arrangement.

We had a few nibbles and tire-kickers who expressed interest, but nothing I took seriously at the time.

I've seen a significant escalation of sites for sale on GFY in the past year or two (as you say - dwarfing potential buyers) - many of which I think are over-priced by unrealistic webmasters who don't take all factors into consideration. I've always considered content to be king - and if it's exclusive to one website only - it adds significant resale value to a website. If the content is widely available on multiple sites, obviously the overall site isn't worth as much - unless the site enjoys a great volume of traffic and good conversion ratio.