Is 10 quid 10 pounds, or about $18 or so? There's a pizza place not far from Berklee I've been to a few times that I rather liked, Woody's, I think - as it happened, I was actually there the night they got the marathon bomber, and it was a mob scene just down the street from there. Crazy night. I don't remember how much their pizza was exactly but it seemed fairly reasonable ands was pretty awesome - wood fired, which is always great.
There's some REALLY pricey places in that area (newbury street is nuts) but ifd you don't mind venturing a little closer to the financial district, there's a small local burger chain called Four Burgers that's pretty awesome that's maybe a 15 minute walk from Berklee. Also, this would be way out of your way, probably 25 minutes on foot, but there IS an Anna's Taqueria past Government Center towards Charles/MGH that's pretty awesome. And if you do Sushi, come to think of it, a bit of a hike but again down in the financial district there's a sushi place called Samurai that has a roll lunch special for I think $10.95 - soup or salad and two good sized sushi rolls, and while there are better sushi places I could recommend, you won't find anything nearly as good for the price.