The DuoLingo Test Center is currently free but it won’t be for long. Give it a try if you’d like to see how it works. Once the DuoLingo Test is accepted at schools and employers, the company plans to charge $20 to take its test.
There’s an established incumbent (monopoly) in this market called TOEFL. If you’ve come to the US to study, you’ve probably taken this test. It’s a lot more expensive than $20 per test and DuoLingo is out to prove it can do this testing less expensively and better.