That explains it... my last car was a Prius.
It seems that Tesla has four very different customer segments:
1) Green types who came from Prius or some older fuel efficient ICE (read: not a luxury car). This group likely focuses heavily on the WH/Mile number, and doesn't really use the high speed, or quick acceleration features very often (or at all). This group will likely not experience any benefit for P85D > P85 and perhaps P85 > S85. This group will likely not experience any benefit from Premium interior.This group probably will care about WH/Mile heavily.
2) Engineer types who came from (whatever -- wide variety), This group will have varying opinions of quickness, speed, and fit/finish depending on their previous experience. This group may or may not care about WH/Mile other than for roadtrips where superchargers are not closely spaced/convenient.
3) Luxury / Sportscar customers who primarily came from Porsche, Mercedes, BMW, Audi. These customers will notice P85D > P85. Most of these customers will notice full leather. This group probably won't care about WH/Mile other than on roadtrips where superchargers are not closely spaced/convenient.
4) Technology enthusiasts - I can't really explain this viewpoint as I fit into this myself, but I also fit into 2 and 3, which I think drives my viewpoint much more, and makes it difficult to distill this group.
For threads such as this, explaining your background along with your opinion will probably display a lot of this.
I will agree though, that $4000 is a huge price for a little bit of leather and some LED lights, but I suspect that they probably also select the "better" leather for premium interior customers which also probably goes somewhat into this price. I would call this type of pricing "Porsche pricing" (as they are well known for having large numbers of very expensive options that seem like they should be standard).