Why the discrepancy between devolo cockpit and iperf

I have set up a Devolo dlan 1200+ network in my home. According to the devolo Cockpit software my bandwidth is displayed at > 200 Mbit/sec. However when I do an iperf test between two computers on the network I only get a throughput of < 40 Mbit/sec.

Can someone tell me why the discrepancy is so large?