Antonyms of adj costless

1 sense of costless

Sense 1
complimentary, costless, free, gratis (predicate), gratuitous -- (costing nothing; "complimentary tickets"; "free admission")

INDIRECT (VIA unpaid) -> paid -- (marked by the reception of pay; "paid work"; "a paid official"; "a paid announcement"; "a paid check")

Similarity of adj costless

1 sense of costless

Sense 1
complimentary, costless, free, gratis (predicate), gratuitous -- (costing nothing; "complimentary tickets"; "free admission")
       => unpaid (vs. paid) -- (not paid; "unpaid wages"; "an unpaid bill")