Comparative form of costly: more costly(adjective)
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Use "costlier" in a sentence
"If truth-in-advertising laws applied to politics, however, you'd have to replace the word "clean" with "costlier" - which is why this agenda is actually very bad news for jobs and the economy."
"This has meant lost orders, delays, or a scramble for alternatives, such as costlier air freight."
"But are the people ready to accept their share of the 'costlier' green agenda?"