At current prices, the going rate for a 7 Day Park Hopper in September is $498 Per Adult. A comparable Platinum AP is $894 3+
Your total for 5 Adults would be $2490 versus $4470. (Plus Tax)
The break even point is at or around the 12-14 day mark. (Depending on how many discounts you take advantage of, but then you're getting into the nitty gritty.) As
@Master Yoda said, the discounts are nice, but only if you make multiple trips. Generally speaking for a 7 day trip, you won't come out ahead.
Also remember only DVC or Florida residents can get the lower level passes with blackout dates. Which means you're probably looking at the Platinum or Platinum Plus Pass.