Thank you for the confirmation LegoSjaak and AndyC!
This reduces the price I would "have to" spend! Instead of 90.78€, the PF parts for the MAERSK plus the track sets would cost me 75.83€. But it is still worth getting an extra 7939 specially since I do not pay VAT when buying from amazon and the set only costs me 107€
So be it! As soon as my first cargo train arrives by mail, I will order the second one, and then the Maersk, and then...