A well-designed frigate can perform many of a destroyer's tasks at lower cost, which matters when a navy has global commitments. The illustrative rule of thumb here is about 60 percent of a destroyer's functions for about 50 percent of the price. Frigates can therefore contribute useful numbers alongside more capable destroyers. The Perry's value depends on the supporting missions it was designed to perform and the fleet operating around it.
Chapter · 6:25-10:56
Frigates, destroyers, and fleet balance
A frigate can supply escort capability at a lower unit cost, allowing a navy to cover more commitments with a balanced fleet.