These ships likely have a unit cost exceeding $50M (considering that they're drone blimps), however the corresponding jet airliner JSTARS has a unit cost somewhere north of $250M. They're used as battle management and command&control tools, and the military branches will very likely want to keep them out of the hands of civilian LE departments due to all the expensive equipment on-board.

The unit cost of blimps vs rotorcraft is likely lower, especially regarding fuel expenditures, and many LE departments have expressed great interest in all kinds of drone surveillance. I would be surprised if these things weren't deployed in high-threat scenarios in municipalities.