If I remember correctly, it'll cost approx. $3,500 for the lawyer to handle annulment cases.
As long as you have married for less than 3 yrs and hv not consummate your marriage, the chances of successfully filing for annullment is rather high. But if you have gone thru the customary or hv shared properties (e.g flat), the chances r slimmer. And annullments cases r possible only when the 2 parties mutually agreed to it.