Well, having run into this exact same situation with an X5 (powers on, no dance, no video, lights flashing), in my case the quote was $294 to fix it.
Now they may quote the same parts (it was gimbal boards and ribbon cables), or they could quote different ones, such as a main board, but I would imagine between $300-$500 to have it repaired.
The ONLY way you could possibly get them to cover it is if it died during a firmware update. Without logs showing that exact instance, with video taken directly before the update, the update logs showing the failure, and the logs showing that the camera still communicates (ie, not a main board spontaneous failure) you more than likely will be on the hook for the repair cost if it is out of warranty.
Before sending it in, be sure to clean the contacts on both the board on top of the gimbal on the camera itself and on the gimbal connection on the aircraft. If that doesn't work, get a hold of an Osmo handle and test it on that (just for test you do not need the X5 adapter, just don't try to walk around and use it without the adapter). If it works in the handle that means the gimbal adapter on the aircraft is at fault.