Yes I have had this Tiered Pricing set on a booking request that I have not had asked for. They took $33 out of my takings. Like a previous person said, of course this does not come out of the guests pocket or AirBnB's pocket. It comes out of mine with no warning and obviously recourse to recover it. They do not care about the host but would like us to go as cheap as possible for more money for them.
Sorry, I do not understand what is Tiered Pricing? Do you mean Smart Pricing? If you do not wish to have it on, you can go to listing->Pricing, and turn it off.
If you have it ON, you can also set a minimum price for the night - so the price will not go under that. You can also set any discounts for long stays.