In my opinion, that's way too high. NADA on this is probably about $5K. For $12,900 you should be able to get a fairly nice 30' AS Excella 1000, even a later year. After 1994 AS went to a wider, taller body style, but still in the classic look. I paid $13K for a nice 1994 30' Excella 1000, and got a lot of AS for the money.
If you are also an Edsel collector, owning a "Squarestream" might be worth the dough, but I think this guy is dreaming. At that price, the unit had better be perfect.
'94 Excella 1000; '03 Silverado 2500HD