If you get out of the Duomo area and into some of the residential neighborhoods you will find a number of good restaurants at very reasonable prices.

One of my favorites is the Bel Aria on Via Meda (I think it is #43 but I might be off by one or two numbers). It can get a bit price (about $45 per person) for dinner but it offers much the same food on a very inexpensive lunch menu.

If you go during warm weather you will have the option of eating in its enclosed garden.