At the very end of the quest to cure Vampirism, the count of Skingrad (the last person talked to in the quest) will reward you (if you are a full vampire, or not) with 1,000 gold (or more depending on your level).
If you continue again to click on the message that asks about a reward, he will keep giving 1,000 gold.

Note: Glitch may be taken out in later versions of the game