since the "offer" was received through Sedo (or did I misread that?), I would suggest they order an appraisal through Sedo to help them determine a suitable offer to make or, better yet, tell them that the "open market" is a fair barometer of value/appraisal system and that you will simply put any offers above $x (whatever the very minimum is you would consider selling for) to auction..... likely won't hear anything back but, if they ARE serious about buying, you have given them 2 options that do NOT involve you paying for the appraisal yourself..... good luck. sp