Why taxes are double than the Air fares ?

The Domestic fares are around 500 and the taxes are around Rs 2000. More than four times. What is the logic behind it. The same is the case with road travel. We pay road tax alongwith the vehicle registration. Why we pay toll for the roads. Frequent traveller pays as much toll as he will spend for his petrol. Dollar price is coming down but the petrol prices are increasing. Are we tsken for a ride ?