I used to spend a lot of time in Belgium and found it an expensive country for technology. Any branch of Fnac that I visited seemed to have prices way above their £sterling equivalent - whether I was looking for ink cartridges, software, cameras, laptops or whatever - they all seemed to be at a premium.
Similarily, smaller independant (?) shops were fairly expensive.
To answer your question, there is no reason not to buy from Amazon.com other than the fact that they may not deliver to you.
On occasion I used Amazon.de for purchases that I could not wait to return home before making a purchase.