The Cargo Dragon development contract appears to have been firm, fixed price:
"A. Obligation
(1) The Government's liability to make payments to SpaceX is limited to only those funds obligated annually under this Agreement or by amendment to the Agreement. NASA may obligate funds to the Agreement incrementally."
https://www.nasa.gov/wp-content/uploads/2015/04/189228main_setc_nnj06ta26a.pdf
Under this contract, which appears to be the master contract governing the per-milestone contracts and subcontracts, Space X would be paid only when milestones were met, and only the amount specified in the agreement. It does not effectively describe "government hand-holding."