If they're successful, I imagine it'll grow to something like that but I'm pretty sure I read (probably on this site) that to roll out, the price estimate was between $8-$25 depending on the day and demand...
$25 for a family of four would still be $100 for attractions that in some cases, are less than four minutes long (let that sink in) but I'm sure if they sell briskly, we'll see the upper limit rise sharply.
Let's look at something important inherent in your statement:
"If successful"... "if they sell briskly"
The argument about G+/LL from many people keeps making two contradictory assumptions:
1 -- It's way too expensive, $100 for a family of 4 for a 4-minute experience!
2 -- Everyone will buy it!
Even if the day of free paper FP, not everyone went through the hassle of grabbing a FP and returning later.. plenty of people just got on the 30-60 minute standby line, despite the availability of free fastpasses.
It is indeed pretty expensive for a short duration ride, especially for larger families. There will indeed be free spenders who have no hesitation to spend $100 to skip a 20 minute line.
But most people will look at the line, look at the value of the ride, look at the value of skipping the line...
What this all means: "If they sell briskly" -- It means that lots of people find it fairly priced. Frankly, if it wasn't worth the price, few people would buy it.
And if it is indeed vastly overpriced, then there will be very few takers.