You’re exactly right. Epic charges the same for games as Steam usually even if their cut is a bit smaller. Plus they still take a cut so the difference would be about 20% instead of 30%. For larger developers Steam only takes 20% so the difference would be around 10%

Considering the fact that you can easily find iTunes gift cars for 10% off face value (and 15 to 20% around the holidays), I remain skeptical that anyone will be paying 30% less.

Fun fact: Brick and mortar retailers spam the checkout lane with gift cards because they do not pay face value for them.