To put it in perspective, the fuel used to launch a Space Shuttle cost in the neighborhood of $1 million, while the cost of the entire launch was somewhere around $500 million to $1 billion.
I decided to fact check you. 57,285 U.S. gallons in a fully loaded 747. Jet-A is 6.84 lb/US gal. That's about 196 tons. Looks like stage 1 of the Falcon 9 is estimated to use 239 tons of RP-1 and stage 2 49 tons.
For the Falcon 9, it costs about $200k for propellant per launch (Kerosene is cheaper than LH2 and the F9 puts about 1/10th as much mass in orbit) while the price of the launch is about $50 million.
Could and real or kerbal rocket scientists here explain why SpaceX isn't doing something like the curiosity rover landing? Sure there's 3 extra steps, deploy parachute, cut parachute, and evasive maneuver, but the fuel saving would massive.
Or put it another way, parachutes are generally less effective than using a system you already have for other purposes. A parachute probably beats a rocket engine if your only task is landing, but when you already have the rocket engine, you're better off using it for landing than building a completely separate landing system.
In short, same basic reason why we use wings and wheels to land airplanes rather than dropping them from a parachute when they reach their destination.
Not "massive". The empty stage is very light, so a little propellant goes a long way. It's less than 10% of the fuel for the entire descent phase (and the optimal upper stage length goes up to compensate somewhat).
