Big difference in fuel consumption for Diesel vs Petrol. Don't only see the price per litre . Look at chemistry wise, diesel burns slower than petrol . Diesel has much more low-end torque than petrol which is critical for heavy vehicles. So you don't have to hit the throttle so much for the car to accelerate.

In Europe, diesel is more expensive than petrol but people there still like diesel over petrol cars due to good fuel consumption.