The prices as you say can be maintained in CRM.
For the cost, you can go to the T-code SCRM. Here, in time sheet integration, you can find the setup for activity type, cost elements.
You can use this node to define your combinations for service type and valuation type.
The rate for the activity type and cost center combination can be maintained in transaction KP26.
If you change the activity type, you can change the rate.
Regards,
Itisha