Giving up parental rights

my husband has been trying for a year to see his two children, his ex-wife refuses to give us a current address or phone number. He pays his child support every month and has tried everything. She is getting remarried and since she got with the new guy she has wrote my husband off as the father.She has asked him to give up his rights and after a year of paying and not seeing his children he is ready, my question is,every attorney we talk to says it will cost about 2500.00 dollars we feel that he has paid enough and got nothing in return is this the average cost for such a thing or is it cheaper if she files?