too good to be true

So exciting or pleasing as to be unbelievable. The asking price for that house was indeed too good to be true—the bank made a mistake when they listed it. I had to ask them to repeat their salary offer because it just seemed too good to be true!

almost unbelievable; so good as to be unbelievable. (*Typically: be ~; become ~; get~.) The news was too good to be true. When I finally got a big raise, it was too good to be true.

So excellent that it defies belief, as in She loves all her in-laws? That's too good to be true. This term expresses the skeptical view that something so seemingly fine must have something wrong with it. The term was part of the title of Thomas Lupton's Sivquila; Too Good to be True (1580).

Exaggeratedly optimistic; seeming so wonderful that something must be wrong with it. This cautious view is undoubtedly even older than its first expression in English, in the sixteenth century. Nevertheless, it has been repeated in the same form ever since, with only such slight variations as Mark Twain’s, “It’s too good for true, honey, it’s too good for true” (Huckleberry Finn, 1884). Shaw played on the expression in the title of his 1932 play Too True to Be Good. See also too much of a good thing.