I moved out here in Novemeber and have had 2 different apartments since weve been here.
were paying a combined total of 350Euros a month for both for everything. Same price at the last place.
Thats a pretty standard "cheap" price for a room. I live out by Placa de Sants, its less than a 10 minute skate to the center, close to tons of non-center spots, and its a pretty rad neighborhood thats mostly spanish types and not as many tourists.
I have some friends that pay 250, and some that pay 500, so 350 is pretty much a standard price.
if youre staying for a shorter time, get a holiday rental - its usually like 20 a night, or 120/week/ person
the best site to find things is Loquo.com its like the spanish craigslist - with casual encounters to lurk on too
hit me up with a pm if you need more help.