New chain plates back from the polisher (bad photo, they really are shiny) .
Per chain plate;
316SS = $10,
Water jet cutting = $20,
Polishing = $30.
Knowing that the damn thing should not split in two for a few years = priceless.
Old chain plates
As stated before, intact chain plates are not an optional extra on a sailboat. Even if your mast does not collapse the rest of your trip will be amazingly stressful.
The problem with chain plates is generally one of access. The actual cost of the items themselves and installation is relatively modest, especially when factored over a 10year+ life. The plan on TIH is to leave the chain plates exposed so that no paneling etc. has to be moved in order to replace them.