Hull the fresh ones, boil the pods, then cook the frozen and fresh peas in the pod-broth. Noone will taste the difference and the savings will buy a lot of asparagus. Use all the edible vegetable scraps in the quiches, and the hard, stringy, or otherwise unservable bits in the soup stock. The same applies to broccoli stems and green onion bulbs. Using bacon as a flavoring instead of the main ingredient in the salad means you can serve twice as much and still pay for walnuts and olive oil for the dressing.
Wafers do have to be made at home.
They are thus more time-consuming by far than purchased bread. But even if the group has to buy the wafer irons, they're still cheaper than the equivalent servings of commercial bread, add more to the illusion, provide more variety, and are better for your group's reputation. Carrots, dried fruit for fruitcake, and enough cheese for noodles baked with cheese simply wouldn't be around in a medieval May or June. Substitute more seasonal foods and you've improved both the budget and the ambiance. It demands more thought, more planning, more careful preparation.