When you finish the cure for vampirism (side quest)(in skingrad so you know )the count will give you the cure for vampirism and 2500 gold pieces (after you take the cure). If you talk to him and you go to the word reward it will continue to give you 2500 gold pieces. Every time you chose that reply P.S NEVER (after the qwest )try to read one of his book's or he will attack you and you won't be able to talk to him again.