What do you mean by non-price material ? Condition record not maintained or material not relevant for pricing ?
If your requirement is first, then system will not allow to save the sale order. If your requirement is second one, then it can be controlled via configuration. For that first you have to list out what are the item categories that are not relevant for pricing. Then you dont assign those item categories to your sales document type in VOV4.
G. Lakshmipathi