IT costs - who has to know them, who wants to know them?

In the past I have several times published thoughts on the ERP for IT, and IT cost management (here and here...). Today I had a very interesting discussion with Econet, a german vendor which adresses IAM more from the process perspective and the ITSM (IT Service Management) area. During this discussion we came across the need for IT cost management and accounting - and to an interesting conclusion:

There is one group which isn't really interested in the real IT costs: The customer of IT. The customer is interested in a fair, reliable, stable assignment of IT costs he can budget. But he isn't interested in exact, always changing numbers.
There is another group which should be interested but in most cases isn't: The IT management itself. They need to know the exact costs, assigned to services and the consumers of the services for planning, for the mentioned fair assignment, for improvement for IT. But most of the CIOs don't really work on implementing a granular, service- and identity-based IT cost management, neither they have it in place.

The obvious question is: Why don't they act? The main reasons are

complexity of the topic
lack of tools
lack of economical knowledge in IT management - most IT managers aren't business but IT people and not all really understand controlling, accounting, and so on

But it inevitable to work on a service- and identity-based, granular IT accounting and cost management and a controlling because it is the basis for IT as a real business unit.

Today's problem is that the ones who need exact IT costs are often not ready for it. And the ones who were ready don't want to have exact but stable, fair cost assignments. But I'm sure that this will change within the next time.