[adjective] -ier, -iestCostly means expensive.Because the fee is calculated on a percentage basis, card holders pay more on costly items than they do on small purchases.(disapproving) Our holiday in Australia proved (= was) very costly.(disapproving) The project was subject to several costly delays/setbacks.
COSTLY
Meaning of COSTLY in English
Cambridge English vocab. Кембриджский английский словарь. 2012