[ken]

> I know someone who got a highly paid job by first doing it for free for 3 months to prove his skills

And I know dozens of people who got burned by being talked into working for "exposure".

[fxtentacle]

In Germany, for such an unpaid internship you will have a contract that says that unless they fire you with a proper reason during those 3 months, your temporary contract will automatically convert into a permanent position. In many cases, it will also already list the salary that you can expect to receive after the 3 months are over. Plus you'll be meeting your future teammates every day in their office.

To me, that is a very different level of commitment by the company than working for "exposure" for someone who has no intention of hiring you.