Didn't feel like a 'discussion' to me when somebody is as condescending as many times as you were in one response. The market for
second hand camera equipment is also based on supply, demand and time of the month amongst other market factors you mention. What sells for £530 at the end of a month when a few people are selling could easily sell for £580 at the start of the month after people have been paid and there are few available...
Basically, to the original poster, The XT-1 and 18-55
second hand is worth what you are willing to pay for it at the time you want it. I still stick by my original valuations and I certainly wouldn't sell mine for any less than the lower end of each scale.