according the the seller's info, this thumb is 6 years old and has only been played for 5-6 hours. this, and the pix,should tell you a couple things.
first, no one lets a thumb sit unplayed for 6 years. it's likely the seller more recently got the bass used at GC - and at GC these sell used for 1100 to 1300. so, he's just trying the get his money out of it.
second, in the pix the ovankol is quite dark. i've noticed that this wood does darken over time as it doesn't have a sealed finish - it picks up oil from hands, etc. this suggests to me that this bass has been played quite a lot - although it may well be in mint condition.
it's probably worth 1300. but, if you watch the boards here at TB, you'll see a newer one for the same (or maybe less) eventually. i got my thumb BO 5 from another TBer this past january; it was less than a year old, mint condition with a new set of strings, i paid 1500.
hope this helps.