Akademik

как в прорву
• КАК В ПРОРВУ highly coll
[как + PrepP; Invar; adv or subj-compl with быть (subj: usu. a noun denoting money, efforts etc)]
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⇒ (usu. in refer, to appreciable amounts of money, energy etc spent on sth.) sth. is completely wasted, has no perceptible results:
- it's money (a lot of effort etc) down the drain (the tubes);
- [in limited contexts](it's) like throwing it (sth.) down a well (into a bottomless pit).
     ♦ "...Им сто твоих зарплат не хватит, дели - не дели, всё равно не насытишь, как в прорву..." (Иоффе 1). "You could pay them a hundred times over, share everything you've got with them, and they'd never be satisfied. It's like throwing it down a well!" (1a).

Большой русско-английский фразеологический словарь. — М.: ACT-ПРЕСС КНИГА. . 2004.