Calculation of Service Charge in PO

Dear SCN's,

Im facing issue in pricing schema, we send material A (Defective) to Service Vendor which he refurbish and send same material A (Usable) for this we follow Sub-Contracting Process. But my problem is in structuring Pricing Schema, here the value of Material A is suppose 100 and I send it to service vendor for which he charges 10 and we pay only 10 to the vendor, this process how to design in Pricing schema because after i designed pricing schema net price is showing 110 but it should be only 10 because we pay only 10. Please help me out with any solution.

Thanks,

Rocky