I disagree. It isn't an exactly equitable comparison, but in function it is a practical comparison. The difference between the top-of-the-line SSD and a standard SSD is, in everyday usage, not that dramatic.
Of course, even the 840 Pro only cost $600 for 512GB... who knows, maybe by the time most people start actually getting these 27" models, Samsung will have a 768GB Pro available.
There is always a premium on having the latest tech, but $1300 for 768GB is going to seem massively overpriced in 2014 (when the one-year Applecare will be over and people can consider dropping in their own 768GB drive). Personally, I'm planning to install a small SSD for the time being and then upgrade it to something more substantial when the prices come down.