Yep. Adding 3X the cost of admission on top of the ticket price for a line-skipping system would reduce park guests and hotel guests (since the reason most guests book a hotel room there is because they're visiting the parks). That would be over $400/day per person before you even get to adding on a Park Hopper. Many guests who still visited would likely look for savings on their vacation by booking an off-property hotel, so it would be a great example of a company shooting itself in the foot. Alternatively, even if attendance stayed the same at the parks and hotels, they would have far fewer people buying that version of a line-skip service and might actually make less money from it than they would selling their $15/person G+ and variably-priced ILLs.
Honestly, not so easy to predict the effect. Too many moving parts.
Let's look at price, plus guest satisfaction for the most the line-skip user, and the pure standby user.
So, let's start with a system with no line-skipping system, at all. This is the price baseline, and let's call the guest satisfaction baseline as 5/10.
Now, we add a line skipping system for $15 per user.
At that rather affordable price, let's say half of all guests adopt it. Say 50,000 people per day paying $15. But with some many people buying it, they can only get a couple passes per day. So their guest satisfaction goes up to 7/10. Meanwhile, it has a severe impact on the lines for non-users. So the guest satisfaction for the other half of guests drops from 5/10 to 2/10.
Compare that to a system of charging $400. 50,000 people aren't paying $400. Maybe, it's only 2,000 people. But charging 2,000 people $400 is more revenue than charging 50,000 people $15. Now, the effect on guest satisfaction:
The 2,000 purchasers can get unlimited immediate line skipping of any ride. Their guest satisfaction sky rockets to 10/10. Meanwhile, since so few people are skipping the lines, the standby lines are barely effected. So the non-user guest satisfactions stays at 5/10.
So, under this hypothetical... which is going to lead to more return visitors, longer trips, etc?
A system that gives 50,000 people guest satisfaction of 7/10, and the other 50,000 are 2/10..
Or a system that gives 2,000 people 10/10, and 98,000 people 5/10?
I'm not claiming to know the answer to that question. Just pointing out that there are many factors that go into the equation. And raising the price, and thereby limiting the number of adopters, can actually increase the level of guest satisfaction overall.