@Sarah113 I'm sorry about your situation, and I understand that you must be frustrated, but you have complete control over how low and how high smart pricing will go. If you didn't set those parameters, it's not AirBnB's fault.
My opinion is that Smart Pricing is only "smart" for AirBnB. They just want the bookings because they make money, and they don't care what your bottom line is. In general, it's not smart at all, and hosts are better off controlling pricing on their own, or setting strict parameters when using smart pricing. There's also software that helps, which I know a lot of hosts use. There are all kinds of rule sets that you can create that can optimize your bookings with prices that are acceptable to you.
You have control of your calendar and control of your pricing. If you don't utilize that, it's kind of hard to place the blame on AirBnB.
Good luck moving forward. Kia