How much could you make scrapping sattelites?

Taking down any satellite that you please would probably be frowned upon. You might be able to start a "trash removal" service that takes down old satellites, although it would require a LOT of certification and development before you were allowed to do so.

The satellites are still private property but defunct satellites are subject to international salvage laws so you could haul them in if you had a working space shuttle and the funds to launch it. Also keep in mind that satellites are designed to minimize their weight since it costs plenty to launch by weight, so you're not going get much by selling aluminum by the pound. You would spend more in launching your rocket than in what you get by salvage. It would be better if you could refit them in orbit, perhaps by launching a repair station with telepresence robots operated remotely from Earth. A pound of aluminum in orbit is worth a lot more than a pound of aluminum on Earth, only problem is there's not much of a market.

Cost!

It would cost a heck of a lot more to recover the satellites than you would get in scrap metal. Although nobody owns any celestial object the people who made and launched the satellites still own them and may well want you to pay them for their loss of use of their functionning satellites.

The reason non-functioning satellites are moved to a "graveyard orbit" or moved to burn up in the atmosphere is becaue the cost of recovering them is prohibitively high.

Space may be an "international area", but satellites are still owned by the countries that built them, launched them, and use them. I don't think any country would look very kindly upon you stealing their property, even if it is no longer working.

Plus, the amount you could sell the scrap metal for would be only a miniscule percentage of the cost to build, launch, and safely return a salvage vehicle to Earth with cargo intact.
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The cost would be prohibitive. Until you develop a runway to orbit transport system getting to orbit will continue to be very expensive