The lead ship is named for Admiral Elmo Zumwalt and carries the hull number DDG-1000. Originally, 32 ships were planned, with $9.6 billion research and development costs spread across the class. As costs overran estimates, the quantity was reduced to 24, then to 7, and finally to 3, significantly increasing the cost per ship to $4.24 billion ($7.5 billion including R&D costs) and well exceeding the per-unit cost of a nuclear-powered ($2.688 billion). In April 2016, the total program cost was $22.5 billion. The dramatic per-unit cost increases eventually triggered a Nunn–McCurdy Amendment breach and cancellation of further production, so the Navy reverted to building more "Arleigh Burke" destroyers.