The trailer itself, assuming it isn't rusted out and is in reasonable mechanical condition, is probably worth $3000. Tire/wheel condition might change that a little.

As far as trailers go the USGI versions tend to be rather heavy. Tough, as long as they aren't rusted badly, but heavy for what they are.

I like the idea of a Bug Out trailer. Instead of having to pack stuff up piecemeal when the time comes you back up, hook up and drive away. If the trailer was light enough it might also be possible to use it as a handcart.