The problem with this pattern is that you cannot charge a customer for something until you settle on a price. So how to overcome this?
Lets start with 1 to 10 sales = $100, and 11 to 99 sales = $75.
Say you sell 9 before deadline... that's easy. Take 9 authorizations only for $100 and mark the orders as paid. Now move to case two, sell 84 for $75. You have to mark the 10 first orders for $100 as paid, and refund them $25 to make $75, and then mark the remaining 74 as paid too at $75.
Can you see your operator of this website pain point? Refunds and manual tracking... Of course with an App some of this can be automated... most of it.. but there is also the time when authorizations expire too.
Anyway, I built out what turned out to be a pretty sophisticated App that functions much like MassDrop and I know that there are some pain points.
It all comes down to charging the credit card, when, and what happens when you do, and ya.. not easy.. but perhaps you can do it!!