well, for freestyle and snowboard you don't need to build anything (only the temporary stands and the Tv rooms are needed)...you just have to "model" the snow on the track (which is normally the same for HP, SS and BA + another slope for Moguls and Aerials...and they're already there, otherwise you only have to throw some trees down to build it), there are no sticky concrete/iron structures, so it's obvious that those are cheap venues compared to jumping hills, sliding track (which is by far the most expensive structure for winter sports, also because of very haigh cost of maintenance during the whole year) and skating/hockey arenas...
p.s. all the official reports are in English, from the first to the last chapter...