If you are making a AAA game in UE4, Mark Rein fully expects you to visit him in his office and negotiate a custom license. That's the way UE1-3 operated. 5% is the default for the masses and for most projects it's much cheaper than a custom license would have cost.
Right, but we're not making AAA games. When comparing Unity Pro licenses to UE4 and others (now Amazon) for smaller game studios, UE4 is still compelling technologically. That said, it's licensing for a small studio like ours if far more expensive than Unity.
My point was basically that Amazon's pricing isn't outrageous, comparatively.