To set back is to delay progress, or to cost somebody a lot. Set back the project, set back by a month, that will set you back a hundred pounds.
The money sense is informal and always jokey about the size of the bill. The delay sense gives the noun setback, written as one word.
1phraseset backTo delay progress; also, to cost someone a lot.
“The flooding will set back the whole build by a season.”
set back is a phrase.
Practised in Phrasal Verbs