free cost
/ˌfriː ˈkɒst/Now rare (chiefly South Asian in later use)
noun
at (formerly also †of, †on, †upon) free cost: without cost, free of charge, gratis.
Origin
Mid 16th century; earliest use found in Thomas Elyot (c1490–1546), humanist and diplomat. From free + cost. With use as adjective compare earlier free. With use as adverb compare earlier free.