Why Why why

Hi , I am wondering why does YBA gear are sell so dirt cheap on audiogon ( like a 7000$ retail amp who sold for 2000$) Because I am planing to buy a yba amp but since they sell for really low does that mean they are peice of crap ? I already own a YBA 2 preamp and im really pleased ( feeding a old Marantz 250 Amp and my mini utopia ) Do you have any Advice of what I can use for the amp preamp combinaison to take the best out of my Mini utopia ?

Thanks in advance.