Definition of cost someone dear or dearly in English:

cost someone dear (or dearly)

Involve someone in a serious loss or a heavy penalty: they were really bad mistakes on my part and they cost us dear
More example sentences
  • On paper they are a formidable outfit but poor decision making and a concession of penalties are costing them dearly.
  • These extended redemption penalties can cost you dearly in the long run.
  • His two losses in a row in the fifth and sixth rounds cost him dearly.
See parent entry: cost

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