If one entity is dependent on another entity which is independent of the table...
If one entity is dependent on another entity which is independent of the table, or a fixed value, where does the fixed value go? It's own table?
If I didn't need to do math with it, I think I would be able to ignore it, but if for instance I wish to find ActualAmt, a field dependent on Price and SalesTax, when the DB user only operates in one state, where would SalesTax go?
If I got the question correctly, either you have to hard code the SalesTax in your program, or put all your constants in a mapping table that can be preset by default values and can be changed by the user through a suitable UI.
BTW, by mapping table, I mean a two-attribute relation that in one column you put the name of the constant and in the other the value.