Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
Because Apple would rather overcharge for the new ones to make the old ones seem comparatively cheap. 😉
 
I was looking at a 13" rMBP 512GB. It appears to be available still, but the price has risen 21%, from £1399 to £1699.

One of the new Touch Bar rMBPs, same config, is £1949. That's a big price rise.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.