It is not true the difference is only 80$. It is approx 200$ + tax in US (260 in Europe) if you just upgrade SDD to 512. Approx 10% increase from the base price is not a minor one - still agree mid tier model is more interesting one if you can afford it.
In the comments below notebookcheck article somebody claims Apple has optimized (undervolting) only 2.4 8 cores processor, not the base one 2.3 8 cores. Can somebody confirm it? Are there benchmark tests difference in MacOS and Windows for 2.3 model?