The cell phone operator told the press the 8GB version will cost 525EUR and for the 16GB model you'll have to pay 615EUR. Both models will be available on Friday, July 11.
The reason why the iPhone costs so much more in Belgium is because tying is against the law in Belgium. Therefore cell phone operators don't subsidize phones but the good thing about it is that you're free to choose which operator and which subscription you want to use.
Mobistar also announced it will offer three subscriptions for the iPhone. For 30EUR you get 200MB data transfer and 3 hours of calling, 45EUR provides 500MB and six hours of calling and for 60EUR you get 1GB and 9 hours of calling.