Quick question for those of you who are 'officially' in business with your lasers.

How do you value your projectors that you've built yourself for the purposes of depreciation and your asset 'pool' value?
Do you simply do it as a sum of their parts, or do you factor in a time element too? As we all know, the part cost of a homebuilt projector is less than its real value...

I'm in the process of trying to get all my books and records in order and I'm wondering what to do about this part?