Unfortunately the guides I could find for Dixon Street (Chinatown) were ten years old and the places no longer exist, but I’ve heard there’s a place somewhere upstairs in Dixon House Food Court with huge plates for average prices.
Outside of this and memories of the Town Hall classic ‘Big Bite’, I wouldn’t know where to start.
I know one place not far from St Peters Station (Mother Yen) that does large meals but I don’t know if you would consider them cheap. They’re relatively inexpensive compared to a lot of places around here.