I don't agree.
Although the Iris pro is more than enough for me, here is my way of thinking that will probably make me buy the high end laptop:
Starting with the low-end retina mbp. I want 16Gbytes of Memory. I am doing some heavy lifting in my line of work, that could use the extra memory. The fact I won't be able to upgrade the memory after the purchase makes me even more sure that I want the memory. For the same reasons I could also benefit from more hard disk space. I want at least 512GBytes, especially if I want to use boot camp.
By upgrading the RAM and the Hard Disk, you have already reached the price of the rMBP, which comes at the same exact (at least here in my country), but also has a dedicated graphics card. So, why not buy that?
However, I totally agree that if you are not a gamer, and you believe that you can live with 8Gbytes and 256Gbytes of disk, there is absolutely no reason to purchase the high-end retina macbook pro.