@MarcoDM, I have received the single module what I could get my hand on it for about 10 Euros. And I cannot pair it with ST. It has some different kind of pairing method, what is not really supported by ST.
Meanwhile I was searching for the topic to reply, I have came across another topic, what should have the reason why it is not going to work with ST. Bummer…
Otherwise, if you want to build your system with Bticino Living Now, then drop me a PM, I am happy to sell the Relay for the price I’ve received it plus shipping, which shouldn’t be too much. It is probably a display model or something similar. The Bticino site list the Relay for 40+ Euros. 
I would take the advice from the other topic and would go with something easier, like the Fibaro relays, you will end up with probably a cheaper solution than Bticino’s modular system.