WLM
This is a very interesting area with many differing opinions and touches on the whole issue of DOC versus DMC etc. I am assuming this is for your own fleet.
Simple way: If you have it, look at your historical data of hours achieved before component replacement or overhaul. Do the calculations and come up with a rate per component per hour.
This should give you a $ per flight hour per component and will include the parts and labor portion of the overhaul. Effectively, what you have is a DMC for that component.
However, swapping between aircraft incurs many more hidden costs, mainly the hourly labor rate times the number of hours to change toe component between the donor and recipient aircraft. Remember to also include the labor cost of re installation of either the repaired, loaned component etc.
Also, remember to include the cost of shipping (if there is any between bases or from the OEM /overhauler) and consumables. Most PBH agreements exclude consumable parts under a $ value ($100-200) and these costs can mount up when making multiple component changes.