Conversion of tenancy to ownership

We are 10 tenants in kolkata which is 65 year old building. Tenants & landlord have agreed for conversion from tenancy to ownership @ Rs.1000 sq feet approx while circle value showing apr Rs. 4500. Huge diff. We had complain to IGR but all in vain. if we do registry then file it return then will get notice from IT for sure as per our CA. pls help