Unrelated to your overall point, that isn't necessarily fallacious reasoning. If most checkout processes in a niche are excessively long (free background check services come to mind) then the customer is choosing to spend extra money now in order to avoid spending extra time with an alternative.

In this case the sunk cost is time, the extra cost is money. So I think it kind of applies. They've just gone with a dual-currency system like predatory mobile games ;)

But I see your point, they're not necessarily overvaluing the time they've already spent, they're trying to avoid doing it all over again.