Unless Amie Street has a patent on demand-based pricing (which would now be in Amazon's hands), shutting down just means the market is open to a fresh, nimble competitor.

Now, said competitor may just end up being bought by Amazon again, true. But until then, they will be a viable "other" choice.

The same goes for every other service bought and modified by Amazon. You're complaining about them, so there's at least a demand of 1 for a replacement service :)