Average personal expenses are about 800 euros per month. This includes accommodation, meals, study materials and travelling in Flanders. Some institutions have student restaurants where they offer meals at democratic prices. (Communistic prices might be better.)
Some institutions offer accommodation at about 200 euros per month. Renting a studio flat is more expensive, although you might find one for 400 euros per month.
Belgium web page
Really excellent observation.
Living in Antwerp