Explanation/Reference:
The cost of collecting the metrics, and the balance between the value they provide and the impact on application operation. If metering code cannot be incorporated into existing components or roles, and you need to increase the number of instances of components or roles just to carry out metering, you might increase costs beyond the savings or income available from metering.
References:
https://msdn.microsoft.com/en-us/library/dn589796.aspx