it's a wonder
It is surprising; it's difficult to understand how. With the amount of expenses we have since the baby arrived, it's a wonder we have enough food to eat! It's a wonder we were able to fit all that stuff into the moving van.
it’s a ˈwonder (that)...
(especially spoken) it is surprising or strange (that)...: Did you see the car after the crash? It’s a wonder that they survived!