What determines the monetary value of a good or service? why are some necessities less expensive than the unnecessary items?

The general theory relates to supply and demand. In such that the costs associated with the overall supply, including managing, transporting and manufacturing of the goods, along with the demand the amount of goods or services required by a given population. When a supply is plentiful and there is less demand, the good or services general decrease in cost. When there is less supply, than there is demand, the good or service increases in cost. So If a necessity is less expensive than an unnecessary item, it could be based on the simply supply and demand issue. Or it could be related to the fundamental costs stated previously, in that in order to manufacture and/or produce the goods or services for the necessity it costs less and there is a high supply to meet the high demand, where there is a low supply to meet a low demand for the unnecessary product or service.

The constant presence of diseases or infectious agents within a given geographic area or population group. it may also refer to the usual prevalence of a given disease with such area or group. it includes holoendemic and hyperendemic diseases. a holoendemic disease is one for which a high prevalent level of infection begins early in life and affects most of the child population, leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do children (malaria in many communities is a holoendemic disease). a hyperendemic disease is one that is constantly present at a high incidence and/or prevalence rate and affects all groups equally. so probably family history.