I don't think I catch what you are asking about the 3 and 4 prongs. But the rest of your question I can address.
It all depends!
what is the quality of the roots? Who is your potential buyer?
Traditionally, an average lot is made up of generally a certain percentage of high end roots to balance out the higher percentage of lower end stuff. The key is to dig only the higher end stuff for highest prices.
If you are in Ohio (as your name suggests) give me a call and we can discuss it further.