this is certainly true in Manchester. as today is steak club day, the club deal costs £8.99 or more in all city centre branches. in Rusholme a mile or so out of town (ford Maddox brown) it's £7.25 or less. many branches like Walkden and Eccles (Salford) are around £6.50. which is superb value for a 35-day aged Aberdeen Angus fresh (not frozen) steak, chips (or jacket ) , peas, mushroom, tomato, or salad. and a drink from a large selection.
but the point applies to most food items , drinks alcoholic and soft. go a bit out of town to save a lot.
some cities have one or two cheap branches. e.g. the lime kiln in Liverpool .