Can’t scale it up. Should scale it down. Not sure if you’re unaware of the costs or are ignoring the because science fiction appeals to you
Scale it up to a billion but then you have to scale up the cost of getting there to about $100,000,000,000,000
In a maned craft, yes. In an unmanned miner robot, much... much... much cheaper.
Snag a small body rich in platinum group metals.