(costlier, costliest)
1.
If you say that something is ~, you mean that it costs a lot of money, often more than you would want to pay.
Having professionally made curtains can be ~, so why not make your own?
= expensive
? inexpensive
ADJ
2.
If you describe someone’s action or mistake as ~, you mean that it results in a serious disadvantage for them, for example the loss of a large amount of money or the loss of their reputation.
Psychometric tests can save organizations from grim and ~ mistakes...
ADJ