Clarification about Conveyance Deed Charges calculation on area or lumpsum

I am staying in Kamothe in one registered housing society with non-co-operation of builder. Our Builder collected money for society formation charges @15000/- for 1 BHK & @ 20000/- total 65 flats for 2 BHK for 26 flats in year 2012 which was total Rs.14,95,000/- is lying with builder only. And due to lease deed old stamp duty difference issue CIDCO transfer charges 4% which govt not collected from old seller, from whom builder purchased plot, hence builder is not ready do the conveyance. Builder is saying members has to pay that difference amount, I will not pay if you required conveyance deed because that fault is not mine. I have paid full stamp duty while purchasing plot from Seller. Now Committee is going for deemed conveyance & decided to collect Rs.49,000/- from all flats, request you whether this calculation is correct for all flats constructed on 2047.11 sq.mtrs plot total 91 flats (1BHK 65 & 2BHK 26). Committee has decided to take further legal action against builder not refunding our money for society formation which was already collected for the same work of conveyance in 2012 from 91 flats.