Put it just after the unwanted gift or price appears on screen, so the refusal answers the reveal directly. Open with Sudden Suspense to build up the item, then use this clip as the verdict, and finish with Nelson Ha Ha if you want the rejection to turn into open teasing.
Über diesen Sound
This four-second clip has Coldmirror saying the German line Das kaufen wir nicht in a flat, dismissive voice, shutting down an excessive present. It feels funny, exasperated and stubborn, turning a refusal into a punchline. It comes from the second episode of Coldmirror's 5 Minuten Harry podcast, a German comedy retelling of Harry Potter, where the line is aimed at the Dursleys and too much gift wrapping.