IMHO, WNW differentiate the kits prices in three (for now) groups: single-seater, two-seater, two-engine. Taube belongs to the second group, and these are priced 119-129USD. And the overall dimension of it makes it belong to that group, too.
Number of wings, decals, etc, does not matter much (Fokker D.VII being an exception) - otherwise the Fokker E series would be cheaper than, say, Camels.