iDTGV

In France, there are the well known TGVs (Tren a grand vitesse) which are, as the name says, trains which run at high speed.  Generally if you buy it in advance the price of a ticket is between 50 and 100 Euros for the common destinations (around 500 km distance).

I've seen some incredible offers for 19-30 Euros for some iDGTV. I was really curious where is the "trick" in this. So I've found this interesting article (take a look at the comments actually):

http://www.zdnet.fr/actualites/internet/0,39020774,39198930,00.htm

I found it interesting to know what is the main difference between iDGTV and a normal TGV. So the answer is "the service".