Estimated cost to replace a speedometer on 2004 Isuzu Ascender

Speedometer sometimes works and sometimes doesn't. It will some time stick on one number like 80 and then go back down to zero and stay there.

Asked by for the 2004 Isuzu Ascender
Very hard to say. Find an Isuzu or Japanese import specialist or a speedometer shop and get an estimate.
If you want to find a specialist, here's a directory link for you: