>Could this material be a cost-effective replacement for stainless steel?

Iron ore costs $~100/ton, The cost of copper ore is hard to find (possibly because there are so many types, and because it tends to be processed locally AFAICT) but you're looking at ~$5000/ton.

So the raw-material cost should be about 50x, and apparently stainless steel costs ~$2500/ton so even if the processing is free you're already 2x the price.

So, no. Copper is about as rare as lithium, for context. Iron is an amazingly cheap metal.