Just a lab to test something regarding OSPF cost.

When I was trying that, I discovered that cost is only applied in inbound direction.

I made a sample LAB to test that :

Loopack 0 on R1 is part of area 0. Path cost is changed on fa 0/0 on R2. If you tried to configure it on fa 0/0, the cost is not applied to R4.

Result :

R4#sho ip osp da summ 1.1.1.1

OSPF Router with ID (4.4.4.4) (Process ID 1)

Summary Net Link States (Area 1)

[…]

  LS Type: Summary Links(Network)

  Link State ID: 1.1.1.1 (summary Network Number)

[…]

        TOS: 0  Metric: 101

Summary Net Link States (Area 2)

[…]

  Link State ID: 1.1.1.1 (summary Network Number)

[…]

        TOS: 0  Metric: 2