costly

Etymology

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

adj

1. Of high cost; expensive.
   a costly activity
   a costly error
   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the rod drive and with the transformers, but were overcome later, and these machines performed useful service until superseded by more modern locomotives less costly in maintenance. 1960 December, Cecil J. Allen, “Operating a mountain main line: the Bern-Lötschberg-Simplon: Part One”, in Trains Illustrated, page 743
   Individual mistakes proved costly for Wigan who, particularly after the half-time introduction of Hugo Rodallega, dominated for long periods. October 15, 2011, Michael Da Silva, “Wigan 1 - 3 Bolton”, in BBC Sport