You can use the solution free of charge for up to 50 Amazon orders per month.

If you exceed 50 orders per month you will need to choose a plan.

You can choose the 'Free 50' plan which allows you 50 orders per month free of charge (any additional orders attract a 1% transaction fee) or you can choose a paid recurring plan that allows a greater number of Amazon orders and attracts no transaction fee as long as you stay within the plan limits.