Hmm. I see BaT price as sale price * 1.05, in order to include fees. Certainly that's how I would calculate it as a buyer. As far as I can tell, this is pretty consistent with what is being described above in the private market. High 80s for nice recent manual Evora GT. Sample size is small, and not inconsistent with higher results for the most desirable cars.
So all the data above makes sense to me and paints what looks to me like a consistent picture. It points to a total price pre tax/reg to the buyer of high 80s for a "typical nice manual evora GT". Of course nicer/less nice cars will go for different amounts!