Raw vs. cooked
On the point about price for raw flash capacity, it's always worth asking what your immediate loss to provisioned overhead will be. For example, what RAID level are you going to implement, and what ratio of data disk to parity will you use? Going with a VMAX deployment, for example, you will lose 25% of raw capacity immediately to parity, assuming you use the recommended 3+1 configuration, which drives the cost per usable GB up into Pure's raw cost territory. Pure is counting on their array logic to bring that price down, and they seem to be able to do so, although with what effectiveness is unpredictable, which would also make Pure arrays challenging to manage, given that one might have a hard time knowing when the array is actually going to fill up.