From an Apple perspective you could easily justify the price for all the old Intel Chip. 1. Intel has a 2 years+ node advantage which you cant get anywhere even if you pay. 2. Intel has the best performance / watt CPU on the market, also highest performance Core on the market, you cant get it anywhere even if you pay. 3. x86 compatibility, which is more like a x86 tax. Although you could get it from AMD.

Now the first two is gone. TSMC has now edged Intel in node, Apple themselves has the best Pref / Watt work in A12X. AMD has proved to be very competitive at the high end. And Intel is still charging Apple the same when they have far less value.

Apple is now being hold up by Intel, but I don't think Apple could dump Intel just yet. There are two thing that is holding Apple up.

Thunderbolt - TB is currently still an Intel only technology. There are no other host controller on the market other than Intel's one. And they cost a fortune ( relatively speaking ) Apple has invested a lot into TB, but Intel is making all the same Firewire mistakes. May be Apple is working on a USB 4.0 solution, and they would dump TB once and for all in 2020. Intel promised to make TB as an open standard in 2018 but has yet to do so.

Modem - Apple relied on Intel Modem for iPhone, which is Apple's bread and butter. Before any move on the Mac side Apple will need to think about its consequences on Modem. In worst case Apple could switch away from x86 and Intel decide to hike the price of Intel Modem. I think the revenue of Modem is roughly the same as revenue of x86 from Mac. Intel 10nm isn't performing. And Apple is not happy with Intel on both front.