One way to do so with IP/information/open source software, would be to give everyone access to just about all IP, but then when a surplus value is not known and needs to be accessed, you give people an option of what they value it. Get a statistically significant sampling group, then pick some percentage of the sampled group should get access, say 95%, and then query them using a Vickrey auction system what their true value is. The people who have the lowest 5% value don't get access to that item for some period. For everyone above 95%, they all pay that bottom 5% price for access to it, not their bid, like a Vickrey auction.
In this way only 5% of the sampled group, which may be 1% of the population lose access, and yet you still get to figure out the range of values throughout the population for that thing because Vickrey auction's incentivize that you bid your true value. Take some weighted average of the bid values and subsidize the IP owner with those funds.
This is what proponents of IP claim. Many even think it is so obvious that there is no need for evidence, but anyway, I'd be keen to see some evidence for the claim.
I can think of a handful of immaterial goods that are not under IP (e.g food recipes and financial innovations). What is common on those is that I am quite happy with the amount available of those immaterial goods (what comes to financial innovation, one might argue that there have been a bit too much of that at some point of our history)
One can infer a smaller supply of art, assuming standard economic assumptions. Some human activities seem to me not to be driven by these assumptions. Stories of artists who create what they seem to be driven to create, not what potential customers want at that moment.
Time is a scarce resource, both for creators and consumers. Some of us get more time than others, but we each get 24 hours per day; in that respect there is equality.
Under what conditions or assumptions might there be "enough" art created and copied?
It’s not a bit more scientific than your argument. I do believe it’s true. But that is precisely my point. Whatever theory underlies IP and it’s benefit to society is entirely based in speculation.
Important to keep in mind that it's not just a tradeoff because it increases marginal cost, it's a tradeoff because it outright restricts the creation of new content.
In creative industries, it means that creators are sometimes unable to build on or adapt creative work to apply to new situations or to expand on artistic ideas. Many market consequences extend from this restriction for better and for worse -- there's a reason why Nintendo games don't work on PCs or have certain accessibility features, there's a reason why backing up save data for many of their games is still a giant pain in the neck, and it's because it's illegal for other companies to create those features for Nintendo games.
IP law also has the consequence of drastically raising the barrier of entry to creating new IP, since assets and universes can't be reused or repurposed without contracts.
And of course, this also has the consequence that certain utility innovations can't happen -- E-Readers in particular have been hobbled for a long time, not just because of patent law but because existing platforms are allowed to make it illegal to transfer legally purchased books into different ecosystems. This reduces market competition in the space, artificially driving up the cost of not just the content itself, but also much of the hardware used to consume that content. There are a lot of things we could build in the E-Reader space around universal annotations, accessibility features like live-reading, etc. IP law restricts a lot of that stuff, you may not build a competing E-Reader that reads EBooks purchased on Amazon.
This obviously has consequences for the market itself; by embracing IP law, we have chosen to effectively kill off and completely eliminate competition in several areas of the free market, while making it illegal to build some meta-layers on top of platforms without enormous amounts of capital and negotiation power.
But it also obviously has cultural consequences since building on top of existing work and sharing cultural experiences (including stories) is something that is basically built into our DNA as human beings.
So we can debate whether there are advantages to IP law and whether they're wortwhile, but I do want to push back a little bit on the idea that marginal cost is the main consequence of Copyright. It's not, Copyright is a choice we've made to artificially eliminate certain parts of the market and to make certain projects and innovations practically impossible to build by anyone other than the biggest players in the market. It's not just about books getting more expensive, Copyright is a system with real tradeoffs, it increases the production of a specific kind of art at the tradeoff of drastically reducing the production of other kinds of art, and at the cost of shaping how art gets distributed and consumed and what things we can do with it, even privately.
It doesn't seem like that bad of an idea, if we take as given that a government service could actually provide as a good of a product as the modern streaming platforms do.
There are other solutions that have been seriously considered or proposed. For example in copyright one idea is to allow things to be freely copied and have some rich entity pay creators. This was how it was done a long time ago, with the rich entity usually being a king or a ruler of a city-state or a wealthy lord.
Another idea is to pay creators via some tax on something that is roughly correlated with copying. An example would be a tax on blank tape.
A problem with these approaches is deciding who gets paid and how much. In the tax approach not many people seem to like the idea of the government deciding which artists should get funded. The usually way to avoid that is to have it based on how many copies are made. But then you need some way to get that data.
You could do it via some kind of polling. That was probably the only way back when copying was mostly physical, such as copying a record to a cassette tape. Nowadays when it is mostly digital you could do it by server side monitoring on download/streaming sites and/or device-side monitoring of playback--but then you are getting into areas that will worry many people for being an opening to more general surveillance.
For ordinary physical goods we don't have these problems--a free market (even the poor approximation of a free market that we have) works pretty good for determining what to produce. But that only works if the goods have certain properties, which copies of art do not have. (If anyone wants more information, look into excludable vs non-excludable goods and rival vs non-rival goods).
The approach of current copyright law is to legally give copies those properties so that the market can determine what art gets produced and how much the artist makes. This is a tradeoff, because it does mean that the consumer pays more for copies than the "correct" free market price (marginal cost of copying).
The other approaches mentioned above tend to make the tradeoff the other way--the consumer pays marginal cost of copying, but less art gets produced than consumers would like.
There's not really any way to avoid having either underproduction or underutilization when it comes to easily copyable art. Once you realize this things make a lot more sense.