Ann: Blackstone Intersects 9m wide Nickel Sulfides at Ban Chang, page-12

Moving from 450ktpa to 2mtpa requires alot more than a second mill, need more banks of float cells, extra holding tanks, bigger rom pad, extra ore crushing capacity, tailings had an extra lift under AMR, but going through 5X more throughput may need to get extra lift now to get it out of the way.
$10m-20m wont go far, before even looking at down stream. We are talking about a significant plant upgrade to get 5 times throughput of current setup.

My guesstimate for downstream alone is $20-35m, factoring in cheaper labour and parts than Oz.