> Musk said that a rocket's first stage accounts for three-quarters of its total price tag, so a vehicle with a reusable first stage can be produced at far less cost — assuming the hardware is fully and rapidly reusable.
~75% savings seems like a "best case scenario" number.
Now for second stage re-use ;)
Seriously though, now I'm just waiting for updates on BFR / Mars mission development progress.
The challenge for SpaceX is to inspect the booster, integrate a new second stage & payload, and relaunch in a few weeks. With a few years of work, it should be almost like a cargo jet turnaround.
ULA's Vulcan plan is to parachute the engines and pumps back, catch the rope with a helicopter, inspect and reattach to a new set of tanks. That seems likely to be a little more complex to me.
~75%.