The retail price of each book is printed on the back cover.
Mail orders involve a post and pack fee.

The first price is Book 1 & 2; second price is Book 3 and 4 and last price is Book 5.

US$4/$5.50/$7
A$6/$8/$9
NZ$7.50/$8.50/$10.50
UK£2.50/£3.50/£4.50