Reasonable cost of construction will depend on the type of finishes proposed (Flooring,type of doors and windows, type of electrical and sanitary fittings) etc. The cost can vary between Rs 900/sqft to Rs 1700/sqft depending on the specifications.
If you have enough time to spare for market survey for selection of brands and purchasing the same, please go for a labour contract. You may think of lot of changes in the construction materials/finishes during construction and you are free to do so if it is a labour contract. In a lump sum contract, you are bound to take consent from your contractor for each and every change in specification, even if it is minor. There are also third party professional agencies available to assist in the selection of materials and preparation of specifications.
I guess we may have to pay max Rs. 1400 / sq ft for the highest quality construction (Marble floor, all Grade A quality for plumbing and others) and i don't think this includes Building registration/approval fee etc. Correct me if i am wrong !
I signedup for contract job (labour+materials) at avg of Rs.1050/sft. An addl amt of Rs.1 lac for marble (contractor provided 2x2 vitrified tiles of rs.45) - Car parking at 80% of cost as nagabalan says the pillars cost similar to room. Approvals, EC, C.wall, water tank, septik tank, sump additional. My total cost is Rs.1400/sft all incl. (incl reasonable wooden cupboards, kitchen racks).