I'll take a stab at it for you. The entire 1970S Proof set is valued at about 6 bucks. The half is the coin to have in the set. I would guess at a shop you could buy the them as follows Cent - 75 cents. Dime - 75 cents Quart. - a buck Just a very generic guesstimate but I think its pretty close. I know I wouldn't pay more for them.
Somewhere around 50 cents to a dollar each. The more difficult part is going to be actually finding someone to buy them.
I would agree that this is about right. I would say that $2-$3 for the whole lot would be about as much as I would expect to see these sell for. People stay here. I know the first couple posts weren't very helpful...but that's unusual around here.