costly

From Middle English costly, costely, costeley, equivalent to cost +‎ -ly.

• (Received Pronunciation) IPA^(key): /ˈkɒst.li/

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costly (comparative costlier, superlative costliest)

1. Of high cost; expensive.

   a costly activity

   a costly error

   • 1960 December, Cecil J. Allen, “Operating a mountain main line: the Bern-Lötschberg-Simplon: Part One”, in Trains Illustrated, page 743:

     In the early days troubles were experienced with oscillation from the rod drive and with the transformers, but were overcome later, and these machines performed useful service until superseded by more modern locomotives less costly in maintenance.

   • 2011 October 15, Michael Da Silva, “Wigan 1 - 3 Bolton”, in BBC Sport‎:

     Individual mistakes proved costly for Wigan who, particularly after the half-time introduction of Hugo Rodallega, dominated for long periods.

• dear, expensive

• costlessly

• octyls