I wonder who's going to sign up to put their cargo on the first refurb rocket? I suppose SpaceX will be offering steep discounts in order to prove the prototype.
A kilogram of water on Earth is worth a few pennies. In space, it's worth $5,000 - $10,000. The value-add difference is the launch cost.
Take a bunch of cheap stuff you'd like to have (but don't need essentially, and can readily replace), and pack it on a refurbed booster. If successful, you've gained a few thousand dollars per kg mass. If failed, you're only out the source materials (and the booster, though since this is a test, it's the outcome that's most significant).
The truly hard part for SpaceX has been getting tthe insurance providers onbaord.