Of course, another factor is how ending copyright might redirect a lot more resources into open source. Without being able to benefit from rents that come from keeping proprietary code, how many companies would switch to using and improving open source alternatives?
It's very easy and simple to pay $100 to use some bit of software. It's way harder to actually contribute to it meaningfully.
Software markets solve a coordination problem. Not perfectly, but reasonably well. Same thing goes for many other kinds of information goods. No way would I pay an author to sit around writing a book, but I'm happy to give them $5 for a copy.
