This sort of thing happens all the time in business. There are a variety of common solutions, for example borrowing and repaying once prices are back to normal again, throttling demand in other ways, raising prices to the customer, cutting costs in other parts of the business, etc. All of those affect the value to the customer in some way. They managed to find a creative way to limit that effect.
In the end, they are cheap, if you are worried about their methods I'm sure they have competitors who approach things in a more traditional fashion and charge accordingly.
In the end, they are cheap, if you are worried about their methods I'm sure they have competitors who approach things in a more traditional fashion and charge accordingly.