I don't buy the claim that copyright law amounts to a subsidy. Copyright law is an enforced monopoly, which is not the same thing.

Of course, you're not focused on the specific works (which is what copyright grants a monopoly on) but on the industry as a whole. So perhaps monopoly on specifics amounts to a subsidy on generalities? But copyright law doesn't have the same effects as a subsidy overall. A subsidy should lead to a higher quantity at a lower price, but copyright law surely leads to a higher price.

(Defenders of copyright usually argue that it also leads to a higher quantity, and I entirely agree with your scepticism that this would actually be a good thing. It's obvious to me that copyright law is bad through and through, regardless of its effect on quantity. Still, anti-copyright activists have a valid point that it's not obvious that copyright actually increases quantity either, since it makes distribution and derivative works harder.)