Well I'd wait for one of the big boys to get here and answer definitively, but until then...
To the best of my understanding, no-one's incline should be equal to their flat bench, all else being equal. Biomechanically, you're at a disadvantage when pressing on an incline bench, that will get worse as you increase the incline, right on up to an overhead press.
Similar to how a front squat should probably max out at around 80% (very roughly) of your back squat max - again, all else being equal (e.g., amount of time dedicated to each, etc.)
I don't know the typical ratio for flat to incline (guess it depends on angle among other things), but anyway, I wouldn't worry about it, unless you're competing in an incline bench comp, lol.
edit: Oh, your incline is heavier than your flat bench? If that's the case, I'd say you've had a training imbalance maybe(?)