There is a free version, but they also have a educator version which allows 30 students to have accounts too. You get additional features with this upgrade. (SUHSD teacher - we have free Classroom accounts for you. Email me for the account info.)
Here is a sample video I have made using Powtoon.
Here is a student sample from an 11th grade English student I found online:
By Eric Chapiewski
Create Commons Attribution License (reuse allowed)