Yar, usually you have to state that the buyer is granted the "rights to use the photograph" for "what purpose" and for "how long".
Pricing would usually differ based on period, type of use... Of course if you grant all rights to the photograph to the buyer, then you SHOULD probably ask for a much higher price.
As for how much to price, photography is similar to a lot of other service industries, you can sell a horrible mediocre picture to a willing buyer for a disproportional amount of money, you can sell a beautiful masterpiece to a cunning buyer for dirt cheap price when there are others who will buy it for 10 times or more. :bsmilie:
So it's always advisable to have a contract ?