RC:
Carrera S base price is 14k EUR more (vs. Carrera). You would be surprised how many customers really care about this price difference. Also, Carrera is only one second slower from 0-100 mph (160 kph) than the Carrera S and from 0-200 kph (125 mph), the new Carrera is basically as fast as the "old" 991.1 Carrera S. Quite impressive.
I still would choose the Carrera S though
but for those who are looking for a nice and "affordable" 911 with less options, the Carrera base model is quite a good choice if you don't go wild on the options. 
My two cents on the topic (driving a 991.1 Carrera 2 pdk and indeed actually caring about the price):
It really depends on what you are looking for, I suppose. When I bought my 991, I have driven both the base model and S (the former one also with the manual gearbox, which to me felt awful in comparison to the manual in my previous 997.1 - but that's another story) and eventually went for the base model.
There was a difference in performance but I already struggle now to use my 350 ps to the full potential. More torque (especially because of the longer gearing) would be welcome but that should have been addressed now with the 991.2 and its turbos. Depending on country, the base model can be more advantageous than the 'S' too. In the "trade off" in picking the base model, I equipped the car to my liking: PSE, Sport Chrono, PASM, full leather, TPMS, sports steering wheel with paddles, 14 way memory seats, sunroof, Bose, Carrera S wheels, PDLS and little goodies (like Porsche crests in the headrests, colored wheel hubs etc). I am still convinced that for me this was a good choice as I actually get to enjoy the equipment more than i probably could use the extra 50 ps.
One final consideration: actually coming from a base 997, and now driving a base 991, the next 911 (no current plans) could very well be a base model too, even if money were less of an object (I am not going to be a hypocrite: if money is not an object, pick the best
you can get). But if it is somewhat of a consideration... Come to think if it: I do not care about have the fastest car on paper but admit it is not nice being the slower car on the road. Then again, public roads are not a race track (and I do not track my car) and I only had rare encounters with faster cars (embarrassing when struggling with TT RS kind of cars
). If you start with the base model and stick with it, you make progress too each time you go for the new model (that I do care about) but at a lower cost (resale value might be less, I am convinced you loose less money overall, as from day 1 you have a lower amount to put down) 