My friend does research in Denmark making these for buildings! I don't really know the details of it but she posts videos  on Facebook all the time. I don't know the cost however. 

I was reading a bit just now and it seems that moss walls like these, the moss is preserved and therefore not living anymore. So you can easily make this yourself. Whereas, if you want a 'living wall' that needs appropriate light and water.

Aha, I understand. I thought it sounded cool to have them alive at home, but then it would be more work. Thanks for the answer! 🙂

I think there must be a way to do it. I also read that it is best to have the moss in dark rooms as the moss will lighten and brown when exposed to light.

I reckon that would be really easy to make yourself in a super affordable way! Could you just use a spray bottle to water the moss?

I don't know. If it's wet like that it may not be possible to glue it to a board using yogurt or egg yellow (which I read the pros use).