Useful english dictionary. 2012.
costful — cost·ful … English syllables
costly — late 14c., from COST (Cf. cost) + LY (Cf. ly) (1). Earlier formation with the same sense were costful (mid 13c.), costious (mid 14c.) … Etymology dictionary
costuolle — obs. (Kentish) f. costful … Useful english dictionary
