Private cloud is more expensive than trad IT storage. Who knew?

Private cloud storage costs more than traditional IT storage and both cost way more than public cloud storage.

That is our summary of recent IDC numbers, covered by Wells Fargo senior analyst Aaron Rakers in his weekly newsletter to clients.

IDC has totted up storage spending and capacity shipped numbers for the first 2019 quarter. The analyst firm provides a breakdown between public cloud, private cloud and traditional IT, enabling us to work out the cost of each kind of storage.

The spending numbers:
Public cloud: $2.813bn (down 14.8 per cent y-o-y)
Private cloud: $2.157bn (up 23.8 per cent y-o-y)
Trad IT: $6.024bn (down 3.3 per cent y-o-y)
TOTAL: $10.994bn (down 2.5 per cent y-o-y)

The capacity shipped numbers:
Public cloud: 51.62 EB (down 20.4 per cent y-o-y)
Private cloud: 8.881 EB (up 11.4 per cent y-o-y)
Trad IT: 31.957 EB (up 17.0 per cent y-o-y)
TOTAL: 92.458 EB (down 7.7 per cent y-o-y)

This means we can calculate the overall cost per EB of public, private and traditional IT storage:

Clearly, public cloud is the best value storage per dollar spent. Traditional IT storage is next, albeit more than three times more expensive. But private cloud storage is almost five times more expensive than public cloud storage and more costly than traditional IT storage.

Why should that be the case? Any ideas?