Extending copyright long after the life of an artist is bad economics. Because of the value of future money any revenue from future sales 30+ is essentially worthless now. So it doesn’t induce people to create more works of art and entertainment.
Promoting artists to create art has long been sidelined as a goal of copyright. Now, copyright is there to make sure already copy written works are profitable forever. I mean think about it. All they have to do is take old music and movies and repackage it as new media. Disney movies from the 30s can be remade today with CGI. Pop music from the 80s can be remixed in 2040, and a whole new generation of people will buy it up, without any artists involved. Copyright has lost its purpose.
I've heard it claimed that Google could have never been started in Europe due to their copyrights laws being so onerous.
Nothing is less constant than the demand for entertainment, and that's reflected in current pricing.
A new blockbuster movie costs $15 in 3D, $12 in 2D.
A month later it costs $6 at the second-run theater.
Three months later it costs $20 on Blu-Ray for as many times as you want to watch it.
A year later it's included in your HBO subscription.
A year after that you can buy the disc for $10.
Ten years later you can buy the whole series for $30.
Forty years later it gets shown as 3AM filler on a cable network you don't pay for separately.
144 years later there are film scholars who have heard of it.
The demand for classic opera recordings is constant. Year after year people will buy the 1966 recording of Tristan & Isolde at the Bayreuther Festspiele with Wolfgang Windgassen singing Tristan. These are reliable moneyspinners for the record companies, you'd expect to see initiatives to extend copyright.
1.07^144 is 17,000.
So, if the album costs $10 in 2018 dollars, it should cost $170,000 at expiration.
Figuring in inflation and conservative returns give 5% per year, so 1125x markup. The album would only be $11,250 in 2018 dollars at term expiration.