As a student, I cook and eat at home most of the time, groceries here are quite affordable and I would sometimes visit the farmers market to get cheap and fresh ingredients. If I feel like eating out, I find restaurants that offer discounts for students with ISIC cards. Tickets for museums and galleries are also pretty affordable with the student card as I can get a discount. As for the most expensive thing in Prague, it would probably be rental and my school tuition fees. But in comparison with other European countries in general, Prague is an affordable city to live and study in.