A couple of things
I worked in a server vendor's marketing department in a past life, and I can say when it came to IDC, we provided or validated information on shipments, but never on revenue. We left it up to IDC to determine an ASP and use that, along with a shipments estimate, to estimate revenue. Similarly, we tended to trust IDC shipment numbers for the competition, but not revenue numbers. We calculated our own revenue numbers based on what we heard for competitors ASPs from our sales field.
I assume Gartner uses a similar approach. So it is possible Gartner seriously overestimated Pure's ASPs, Pure's shipments, or both. So if Pure, as a start-up, is aggressively discounting to grab market share, and Gartner assumed something different for SSA ASPs, that could explain part of it. But it does not explain why channel checks did not reveal any potential errors in shipment numbers. For that matter, did Gartner do enough talking with customers? Or does Gartner not listen to their customers?
Regardless, this is a serious black eye for Gartner. "I got it wrong." What else has Gartner gotten wrong? They need a top to bottom scrub of their market share analysis and impacted reports (which include the MQs). Gartner should offer refunds or significant discounts for renewals to their customers.
Also, this HAS to impact the "Ability to Execute" axis of the SSA MQ for Pure. Ability to Execute is in large part derived from sales success. Gartner must republish the last two SSA MQs.