This is all pretty misleading Iainm. Le Snow Factory is actually called "L'Atelier de la Neige" (The Snow Workshop). They don't make any snow there, it's a pumping / compressor station that supplies the snow cannons on the mountain with water and compressed air, there are hundreds of these in the alps. The building also houses the computer control system that controls the operation of the snowmaking equipment and a workshop.
You can go on a guided tour round it with Pierre Mattis who is head of snowmaking at
Val d'Isère http://www.radiovaldisere.com/index.php?p=vids&year=2015&month=01 just click on the photo of the pumps on the left. As you can see in the video the machinery is not housed in a "hanger", but in reinforced concrete machine rooms that are located underground. If this is a new build €3 million would be very cheap, I think it's more likely that they have upgraded the existing facilities.
The amount of snow produced will vary according to temperature, under optimal conditions the pumping station is said to be capable of providing enough air and water to make 2000³m of artificial snow per hour.
In order to reduce the operating costs they have installed ABB variable speed motors to drive the high pressure pumps that feed the snow canons, these use up to 50% less electricity than conventional motors, 80% of the cost (€360, 000) was covered by a grant.
If you want to see a 'snow factory' you will have to go to either the
Pitztal glacier or
Zermatt where they have installed IDE all weather snowmakers
http://www.ropeways.net/aktuell/ide3/index.htm
Or visit the TechnoAlpin factory, they make one that fits in a shipping container
http://www.technoalpin.com/en/snow-guns/snowfactory.html