You should also decide on the factor of how much kilometer your daily/monthly drive is, you will be saving a lot on fuel on Prius if your daily run is 50km or above. I don't know both car mileage per kilometer but if i take 20 km/l for Prius and 12km/l for Altis with monthly driving of 1500 km you annual would be 1500 * 12 = 18000 kms/ year, 18000/ 12 = 1500 liters, 18000/20 = 900 liters, with current price of 78.84, 1500 * 78.84 = Rs. 118260 on Altis per year, 900 * 78.84 = Rs. 70956 on Prius per year, so you save Rs. 47304 per year.
If your monthly running is 3000 kilometers you will save more than Rs 90k per year with Prius.