[Lynn Eades]

Matt, Your casting price seems incredibly high. I have had brass (gunmetal?) plates cast, and they would not have come anywhere near that price.
I didn't have to have a run of them done. I had two of each, done from two sample plates (over a number of years) followed by the last pair about 3 years ago (6 plates, total) and the foundry made a pattern to my requirements and I still have the pattern. Unfortunately I would have trouble finding accounts and don't recall the prices.
I also had some aerial bits done that now adorn the odd carrier, here and there, around the globe.
I would suggest you try a few more quotes. You might be pleasantly surprised.