Not every quote needs a second look — but a few specific situations make it worth the extra day of waiting.
A second opinion costs you time and sometimes a small diagnostic fee. It's not worth it for every repair — but for a handful of situations, it consistently pays for itself.
Above this range, the cost of being wrong (either overpaying or fixing the wrong thing) is large enough that a second, independent look is cheap insurance.
This framing isn't always wrong, but it's a common pressure tactic when it is. A second shop can confirm the safety claim without the same incentive to make the sale.
These are the two most expensive repairs a shop can recommend, and also the two where "rebuild vs. replace vs. it's actually a smaller part" disagreements are most common between honest mechanics.
If a shop diagnoses something that doesn't obviously connect to what you actually noticed (a noise, a warning light, a performance change), it's reasonable to ask a second shop to independently reproduce the same finding before you approve the work.