I'd say the shifter cable guides are more indicative of the age than the water bottle bosses. Late 70's to early 80's? What diameter is the seat post?

Value - I think it's worth what the frame and crank would go for - $300 to $400. $600 would be a hard sell, but not out of line if it was fully Campagnolo equiped, was Celeste, and had better decals. It's my size too....

edit - I do see a Piaggio decal there as well....could it have been repainted by a Bianchi dealer, and that decal was added along with the poor location downtube decal? Seems like an odd combo of 'details' on that frame.