TL;DR The maximum number of copies that society should pay for a particular title is the number of concurrent readers, watchers, or listeners of that title--this is the theoretical limit of copyright compromise. This may be possible within current copyright law, as long as co-operation can be organized.
We have two opposing forces in the modern copyright battleground. On the one side is copyright maximalists--usually the middlemen--who want to maximize profits and minimize (or at least have little concern for) public good. On the other is copyright minimalists (i.e. the public) who are now part of the distribution system called the internet. Maximalists want to maintain artificial scarcity while minimalists (most people) want to (a) share what they will with friends and (b) not feel guilty for exploiting authors.
According to my understanding of copyright law and the first-sale doctrine, content producers and publishers presently make more money than they theoretically should. They rely on many copies of their title becoming "dead" copies, never to be used again--for instance if you buy a book, read it, and put it on a shelf, that becomes a "dead" copy. But because a person has the right to both buy and sell a copy of something, they have the opportunity to co-operate to minimize publisher profit. Can we set up a public service to minimize publisher profit and maximize public good?
Let's take a book as an example and follow it through a simplified publishing lifecycle. Let's say that on opening day, 10,000 people buy the book. For the sake of argument, let's say that all 10,000 finish the book in 7 days. There are now 10,000 people who have read the book, no longer need it, and are willing to sell it given an opportunity. If this book is a particularly good one, the 10,000 initial readers probably will turn to their friends and recommend it, causing more demand. A second wave of readers arises (both from demand caused by advertising as well as "word of mouth" from previous readers) and now in week two, 50,000 people want to read the book. 10,000 of the 50,000 copies needed can be satisfied by purchasing the first wave's copies, while 40,000 must come from the publisher (or author) directly. Now, let's say that 50,000 is the peak interest level garnered for this particular book in any given week--in the following weeks, fewer people are interested in reading the book, perhaps 40,000, then 25,000, and finally 5,000. Perhaps it flatlines at 5,000 people per week. With 50,000 copies of this book in circulation, each subsequent wave of readers can choose to buy it from a previous reader (rather than the publisher) because the number of copies sold exceeds the current number of interested readers.
Something rarely conceded by copyright maximalists is that early adopters are also early advertisers. As mentioned in the example above, if they like the book and recommend it, they contribute toward increasing demand which directly benefits the publisher (and author). In today's arrangement (where most copies are bought directly from the publisher) there is no recognition or payment made to early adopters even though they play a very valuable role to publishers. This situation could be remedied through re-sale.
Imagine a re-sale marketplace that treats all copies as equal, but enforces a round-robin selling queue: when new demand for a title (book, movie, song) is introduced, the earliest adopters (readers, watchers, listeners) have their copies sold first, followed by later adopters, etc. From the perspective of the beneficial role that early adopters play, it makes sense that they should be rewarded--if you find a good book first, your reward is to enjoy it first and to do so for free (or nearly free) by then re-selling it.
It's also interesting to note that eventually, as long as the book has a trickle of demand on the tail, earlier adopters would continue to be paid back, i.e. if you buy a book that is popular or that will become popular, you're all but guaranteed that you will be able to sell it again, eventually. In effect, what this means for individuals is that rather than needing an annual budget for media consumption, he or she needs an initial capital investment to put into a rolling media purchase fund, since purchases are eventually paid back. (The more sustained demand for a title the shorter the period of time between purchase and re-sale).
What we need for this kind of marketplace to work is for a single company or non-profit to act as a purchaser-in-behalf of consumers. This purchaser-in-behalf would have a large library of many copies of titles. Perhaps it has enough copies of the particular title you're interested in to sell a copy to you. Or it may not. But, rather than purchasing something directly from Amazon, you would point the purchaser-in-behalf at Amazon and say "I want this book, buy it for me if you don't have a copy". Thus, you would immediately get a copy of the book and its source (whether someone else using the service or Amazon) would be irrelevant to you as a consumer. And then if your particular "reading" of the book did require a new purchase to be made from the publisher, that copy of the book then becomes a public good because it increases the total possible number of concurrent readers in the re-sale system.