Since Pak asked for it and Oman offered it to India, India might have thought it as conspiracy to trap India into buying something that wasn't of any value at that time..
I still don't think gawadar would have given something to India economically but yes it would have paid them off strategically, as we know that gawadar for Pakistan wouldn't have any meaning to Pakistan if China's economic interest weren't vested in it, unless Pakistan itself was able to build this port and road links to it and had asked other countries to use this port and pay the rent..