I am boggled by apples upgrade prices...
I'm hoping they'll have more reasonable upgrade pricing once they release the 2016 model. I think those SSD prices reflect 2012-era costs and Apple is reluctant to change pricing strategies between redesigns.
I actually think holding on to old pricing models makes sense. It tells people not to wait for a better deal, because one isn't coming. It's the same reason they don't announce new models far in advance of their release, which in turn is why smart shoppers (like us!) look to rumor sites to better plan our upgrades.