Your third paragraph, assumes that ocean ores would only be used for carbon negative products, which unless we want to lie to each other we know it’s not true and we will use them to make the frame of the iPhone or the trim of a Tesla, or some random shape in the name of art. Then we’ll be “oh, dang, that didn’t fix anything AND it added MORE carbon not only in the atmosphere but to the ocean”
you can make this assumption if you believe refined metals are fungible.
If making refined metals cheaper, it will also mean more of it available for green tech (that currently might be too expensive to produce to replace fossil fuels). On the other hand, more available metal ores do not make fossil fuels more economical (also an assumption, but i think this is fairly true).
Therefore, on the whole, this would make green tech more competitive with fossil fuel tech.
