What are some of the least expensive options for someone whose dentures won't stay in while eating even though they fit and are "glued" in?

See your dentist: Dentures not only have to fit but function harmoniously. If one area is hitting first, it causes the dentures to become unstable. Other causes include grinding of teeth or other oral habits. The least expensive way is to have your dentist check the bite. There are other options including relining of your dentures, new dentures, and implant retained dentures.