If you are looking for jewelry repair shop with reasonable cost in Tokyo, I would recommend this shop.
They provided professionally skilled repair work on broken neckless chain with good services. The cost I paid was super reasonable though they didn’t hang any signs. You could ask the repair cost beforehand, of course.
To visitors: Okachimachi is the place where a lot of jewelry shops located with variety of selections and there are also repair shops around there. I encourage you to stop by and check these shops when you walk along Yamanote line between Ueno and Akihabara.