Cost alone isn't the single determining factor in the choice of modern Airlifter. A-400M is proposed to replace C-130 type transporter because of its increased Payload, Range and Endurance.
The point is Pakistan doesn't need the range or the endurance the A400M offers (needed for force projection). The C-130 is more than capable of carrying a good payload along the North-South axis which is no more than 1000nm at most.
Further, C-130 operating costs are lower as the training and maintenance infrastructure is already in place and there will be plenty of spares in the market for decades to come.