Onlinemetals.com seems to feel it can charge about twice what McMaster Carr does per square foot for 410. The biggest difference is that onlinemetals will sell it in wider sheets, which I may have to use for the breastplate. I ordered what should be enough for sabatons, greaves, and cusisses for $90 from McMaster Carr. 8 square feet of 0.029 and 4 square feet of 0.04. Hopefully my estimates are OK. These are a touch thicker than I've used before, but that should make it a bit easier to make smooth even shapes and give me a bit of margin for grinding.