Most docs are available through Pacer. Pacer pricing is $0.10 per page capped at $3 per document. Buying everything would cost a lot. In addition, new case law is continuously being created. So you couldn't buy everything and be done with it.

You can republish... court docs are in the public domain. RPXCorp tried doing this with patent law. For a time, they made everything free. That practice didn't last and they now pass on their costs to customers.