The rMBP's SSD can be upgraded where have you been? It has a SDXC Card slot and there is an adapter if you really need an express card slot. The rMBP also has an hdmi port 2 USB 3.0 ports, 2 thunderbolt ports, better video card, its thinner and lighter. You can also change the resolution if you need more workspace, and a 15" 2880x1800 retina IPS display with much superior colors and contrast..........
Yeah I know the rMBP RAM can be upgraded.... at time of purchase, costing more than a set of SODIMMS. RAM isn't user-upgradable. SSD can be upgraded at time of purchase, or after if you want to void your warranty and give over your firstborn to pay for it.
The point of my post is that the 17" cMBP still has advantages over the rMBP. It depends what you want out of a machine.