Aside from collectibles and science, the point of asteroid mining isn't to bring stuff back to Earth. It is to replace the high cost of launching stuff from Earth.

Let's say the Starship rocket works as intended and can fly for $20 million a launch. It takes about five tanker flights plus the cargo launch to get ~120 tons to the Moon's neighborhood. So $120 million for 120 tons is $1 million per ton. If you can mine usable products from asteroids for less than this, you come out ahead.

Metallic asteroids contain about 15-50 parts per million of the "Platinum group metals" (the ones below iron, cobalt, and nickel on the Periodic Table). Parts per million is the same as grams per ton, so 15-50 grams per ton. Average PGM price is around $50/gram, so market value is $750-2500/ton.

They are alloyed with the three base metals as ~90% iron, 1% cobalt, and 9% nickel (the proportions vary by sample). So first, you have to extract the PGMs from a chunk of iron alloy, and second a little added carbon turns the iron alloy into a decent steel alloy. There are other asteroid types (the carbonaceous ones) with carbon, so that's not hard.

Now your ton of metallic asteroid is worth $1 million for structural steel in space, because that's the launch cost you avoid for not launching structural parts from Earth. The value as structural metal is worth way way more than the small amount of precious metals in it.

You can try to separate out the PGMs before leaving the asteroid, or afterwards so you can use both the iron alloy and the PGMs, but I highly doubt you can process it in space for the $750-2500/ton market value. For comparison, the price of hot-rolled ordinary steel on Earth is $775/ton right now.

Look when we discover Pandora we will need to be ready