Hi,
as you probably know, the metric in OSPF is defined as the cost of sending a packet on a particular link and a router advertiseses this cost as the link cost for this interface in it's update packets. Cost is assigned on a per-interface basis and there is no differentiation between the types of OSPF routes in the calculation of the metrics (E2/N2 are special cases) - the outgoing cost of the interface is always part of the total cost of the routes pointing to that interface. Another special case are Point-to-Multipoint interfaces, the Cisco OSPF implementation allows you to assign different costs on a per-neighbor basis here.
If this doesn't answer you question, could you elaborate a bit on what exactly you're trying to achieve, perhaps with a small example that gives us a better understanding? Also keep in mind that there is a preference rule based on LSA-Types for the best route selection in OSPF and this rule has always precedence over cost or distance (in the same process).
Thanks,
Rolf
