The costs of piston-and-jet aircraft

Were mixed piston-and-jet aircraft a cheaper or more effective design choice?

They could supply burst speed for a specific task, but their two propulsion systems made design, maintenance, training, and logistics much more complicated.

The Ryan FR Fireball used its jet engine for the burst speed needed to intercept kamikazes. That extra performance carried a steep penalty because two dissimilar engines required different installation arrangements, maintenance, training, and stores. Once purpose-built jets could provide the same performance, the mixed system became difficult to justify. A narrow performance solution could create a disproportionate support burden across the fleet.