I strongly disagree that a modded player is worth less than a stock player, especially if done by someone with excellent credentials: Modwright, Exemplar Audio, RAM, etc.
However, the used value of the mods is a fraction of their original cost. Assigning a percentage is of little value. I would recommend watching the listings for a model you are considering and noting the units that sell quickly, and their asking prices. These will have been priced correctly.
If a unit lingers in the listings, you can be certain it's priced to high.
However, the used value of the mods is a fraction of their original cost. Assigning a percentage is of little value. I would recommend watching the listings for a model you are considering and noting the units that sell quickly, and their asking prices. These will have been priced correctly.
If a unit lingers in the listings, you can be certain it's priced to high.

