You are renting access, not buying a thing. The charge repeats on a date you agreed to once and will probably never think about again.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
renting the apartment instead of buying it.
For example
You pay every month and use it constantly. You stop paying and it all disappears, because you were renting the whole time.
This is one card out of 275.
The hundred words you meet most are free — the whole set, animated, in one file that works with no internet.
Volume 1 has all 275 in fifteen chapters, with Staying Safe the largest chapter on purpose.