The price seems about right -- if slightly high. The Webers and the gauges probably helped it get up there. I've seen a couple listed somewhere (ebay perhaps) in the $40K's.
By the way, the Modena is not supposed to emulate any one Ferrari, so I think the "how authentic is it" question is kind of moot.
It is a roomy car (much more so than a Cobra) -- I sat in one at Knotts a few years ago, and has won various kit car awards for quality of construction. I think you could duplicate one for close to that figure -- and you could say "yes, it's an original -- original Ferris Buhler car!
Ben