Repair is considered too expensive when the cost to repair the vehicle exceeds the MEL (Maintenance Expenditure Limit). The MEL for any vehicle can be found in the technical bulletin for that particular vehicle.
The current regulation is: AR 735-5 Feb 2005. I believe you are interested in chapter 13.
Be aware of the following stipulations posted on the APD website:
* * * Special Notice * * *
Paragraph 13-3 of the 2005 edition states—
“Process the financial liability investigation of property loss in accordance with the version of this regulation in effect at the time the LDD occurred.“