It would probably make more sense for copyright fees to be proportional to the revenue the company makes. Disney paying $500 to license Mickey Mouse after 5 years while making millions isn't equitable for a small business copyrighting a toy brand for instance.
I'd be open to there being an additional cost based on total revenue earned, but the scale should be the fixed costs, with significant additional revenue just moving that number up.
I think the goal for the financial cost of the extension to be roughly equal to the "harm" caused to the rest of society for locking it up. So, I think making the scale in some way proportional to revenue could be a rough proxy for "how popular is this thing", which is then a rough proxy for "how much does it harm society to lock it up for 5 more years".
That said, I'm more interested in being equitable to _society_, rather than being equitable to _creator_. Copyright should be just good enough of a deal that it encourages creative works. It doesn't need to do more than that.
