too good to be true

used to refer to something that exceeds one's expectations in such ways that makes it hard to believe

The idiom "too good to be true" has its origins in English idiomatic language and is used to express skepticism or doubt about the authenticity or viability of a situation or offer. It is used to convey the idea that something appears exceptionally favorable or positive, but the speaker finds it so incredible or unlikely that they suspect it may not be real.

When he heard about the job offer with an unbelievably high salary, he thought it was too good to be true.
The online advertisement promised a "get-rich-quick" scheme that sounded too good to be true, and most people avoided it.
The deal on the luxury vacation package seemed too good to be true, leading travelers to suspect hidden costs.
She was wary of the too-good-to-be-true investment opportunity and decided to conduct thorough research before committing.
Hearing about the diet that claimed you could eat anything and lose weight sounded too good to be true, and nutritionists were skeptical.