Trash is never really trash - you can always do something with those resources, the only problem is that nobody wants to do something with it now.

You can imagine it might actually be pretty profitable to buy landfills when you're, say, a plastics manufacturing / distributing company, because the land is super cheap and you can literally dig plastic from the ground to sell to others.

No, our trash should be recycled as much as possible and where not possible try to avoid those materials. Plastic is one of them.