I'm not sure why they should be worth less. We have a 4255 that came from England or Germany. There are about 4 things that you could look at to tell it is different than a US machine.

1. It has a Park Brake, which is simply a disk brake on the drive line.
2. It has a separate button in the dash for warning lights.
3. It has full size black fan shields.
4. The light wiring under the dash has been butchered a little bit when they switched the lights over to NA style.

I fully intend to fix the wiring, and it has the same exact wheels as a NA tractor would. It has about 11k hours on it, have had it since 7k or so. As you mentioned, it is pretty easy to spot the difference from a tractor with 10k hours to one with 20k hours. Why should it be worth any less than a NA tractor with the exception to the wiring?