Everyone IS making money out of thin air. That's the catch. There is no catch. Just like Bitcoin and the US Dollar, Steem springs to life out of thin air.
When 12.5 new Bitcoins are mined every 10 minutes, they just appear out of thin air. That's approximately $8000 of new Bitcoin being created ever 10 minutes or about 1.1 million US dollars every day. The price of Bitcoin doesn't go down every day because of the newly created Bitcoin because people want to buy the newly created coins. There is demand for the new Bitcoins.
The Federal Reserve does essentially the same thing when it creates new US Dollars. Only it's network of miners are the Big Banks who take the Dollars the Fed created out of thin air and loan it out to businesses and consumers who want it to buy goods. They demand the new Dollars to make purchases.
The only real difference between Steem, Bitcoin and the US Dollar is how it's distributed. Since Steem is distributed to people who earn it by by using Steemit. Since Steemit is a sort of feedback loop (the more Steem you have, the more Steem you can earn) demand for Steem is created. And like other currencies or coins, where there is demand, there is value.