expression
things don't always go as planned; it's not that easy; the wholesaler won't sell it like that
Idiomatic expression meaning that things rarely work out as smoothly as one hopes, often used to temper expectations. The literal image is of a wholesaler refusing to sell goods at the buyer's desired price or terms.
そんなにうまくいくと思ったら大間違いだ。そうは問屋が卸さないよ。
If you think it'll go that smoothly, you're mistaken. Things don't always work out that easily.
彼はすぐに昇進できると考えていたが、そうは問屋が卸さなかった。
He thought he'd get promoted quickly, but it wasn't that easy.
The phrase originates from the image of a wholesaler (問屋) who refuses to sell goods at the buyer's desired price or conditions, symbolizing that things in the real world do not go as conveniently as one might hope. The exact historical origin is uncertain, but it is a well-established Japanese idiom.