There are some scammers around in FS/FT, it seems
Lots of n00bs selling stuff, some buyers getting scammed. Be careful and follow the guidelines for selling and buying, if something is too cheap think twice.
Similarly, if someone is too willing to drop their asking as far as you like in double quick time, think twice! These people are out for a quick profit, and £40 in hand is better than holding out for asking.