Take a look at
http://www.booking.com/ for all ho(s)tels with their prices...
Diners in a restaurant are not that expensive. When youu go for a simple 1 course meal, it will cost you around 15-20 euro.
edit: eheh just thought about this, if you want really cheap)
buy a cheap microwave(40euro) and buy ready made(fresh) meals at grocery stores for 3-6 euro's....