This is the headline "Musk says that in 10 to 20 years, work will be optional and money will be irrelevant thanks to AI and robotics". The article... " http://tiny.cc/ezuz001

Anyone who has followed Elon's career will know that he's almost always over optimistic in this time-frames. So 10-20 years is probably closer to 15-30 years.

What he's talking about here is an extension of the theory of Superabundance. The idea isn't new having been covered in the book 'Superabundance' by Tupy and Pooley which talked about an "Infinitely Bountiful Planet". This was in turn derived from the work of the economic great Julian Simon (he of the Ehrlich bet) which is summarised in his book 'The Ultimate Resource', (meaning humans). The notion goes back even further to Azimov who prophesied a planet where all human needs were completely fulfilled with minimal effort.

The idea revolves around Simon's calculation of Time-Price. This is the amount of time someone has to work to obtain a given good. The most startling example of that was that, in 1800, the average worker had to put in 5 hours of labour to earn enough for one hour of after-dark light via candles. Now they must work less than 1 second to run a light for one hour. Using similar methodology, lamb is 85% cheaper (in terms of Time-Price) than 1980, Salmon 81%, Coffee 74% etc etc.

As things become increasing cheaper to make, the amount of work time required to buy a representative basket of goods in 1980, ifs cut by 2/3rds in 2025. So, people work less to get the same amount of goods and as robots and AI make work even more productive, the work required to meet the average needs of the population plummets to the point where it is effectively zero.
I don’t think any of us on this forum will be around to see it (although medicine is advancing at a comparable pace to other industries) but what a world it’ll be. Ordinary people in 2060 living a life the richest of the rich only dreamed about in 1960.