price hike for Antwerp newcomers - illegal?

http://www.xpats.com/en/headlines/minister-condemns-price-hike-antwerp-n...

"Belgian Interior Minister Joëlle Milquet (cdH, pictured) has launched an investigation into the decision of the City of Antwerp to have its immigration department charge a €250 registration fee for non-Belgians. Antwerp’s city council decided last week to increase the one-off payment from €17 to 250, to "cover costs". According to Antwerp Mayor Bart De Wever, "each new registration file comes with a price tag of €330, when you take into account all the IT costs, document validity checks and contacts with the Immigration Service." Milquet told De Standaard that she condemns the increase but will await a formal endorsement by the city council before requesting an official analysis."

Surely, this must fall foul of some provision of the TFEU? It seems blatantly discriminatory to me, either free movement of persons or equality provisions must be relevant. Opinions?