You seem to like your existing supplier and have a good relationship with them. It is difficult to put a monetary value on that , but is is considerable.

I had a similar experience with a German supplier a few years ago and the customer told me afterwords that he was very sorry to have changed to them, it cost them an extra 70,000 euros in questionable damage in just 18 months. He was very happy to return and I hope we will have them ever more.

My advice is if you are happy STAY WHERE YOU ARE, there is nothing for nothing even if you are Toyota. Even they have to pay wages , costs etc like everyone else and have to recoup things somehow. You will pay eventually , you have to.