Conveyance Deed

We have a residential flat which we purchased in 2007 on resale in Seawoods area (Navi Mumbai). The building in which we are staying was constructed more than 20 years ago. Society formation and OC is done but conveyance deed is not yet done. Now the society committee members are proposing to get the conveyance deed done and they have informed us that those flat owners who have taken flats on resale have to pay 2 lakhs or more (depending upon the number of resales of the flat) to CIDCO. We also have shops on the ground floor of the society and the shop owners who have taken shops on resale have been told to pay a much heftier sum. My query is: If the conveyance deed was not executed in so many years and now the society wants to get the conveyance deed done, should not all the flat/shop owners be charged equally? Why should only resale flat owners be liable to pay? If there is any such clause to explain the charges, I request you to please share so that we know what are the charges for a conveyance deed and who is liable to pay it