it's going to cost $300 to get my somewhat exotic automatic wristwatch serviced.

this one.

that's expensive.

Apparently they are rebuilding the movement and recalibrating it. Takes 2 weeks just to calibrate the movement

Is it not keeping good time or not working at all?

Swamp Daddy : it intermittently stops working. Moisture must have gummed up the jewels a bit

It's a 30 year old watch. Probably time for a good cleaning anyways. Also includes replacing the crystal