Quoted from Bok013:
Except for when I shoot the ball of the right ramp the fault opens and closes a couple of times but then it stays closed.
I had the same issue with my ES.
I had to take the mechanism apart, clean it and readjust the spring (I think).
If the plastic part is not broken, a simple cleaning and reassembly may fix it. If I remember correctly the spring tension is key. It looked to me that the part is fairly insensitive to wear, and still operate as designed.
The worst part about it is that I had to remove the playfield from the cabinet to get at the assembly. I don't think you can work on it very effectively when the playfield is still installed.
As for the cost, I can see 1 costing maybe $60 or so, but if you made 30, I don't see how they would cost $2000.
The key may be to find a hobbyist with a mill that would make a few for $50.
If you wanted a run of more than a few, then find someone with a CAM system. Perhaps draw up the part on CAD and supply it for their system to make.