Once you have tried the translation to the first language for free, in case you want to add new languages, and continue using Glotio, it will charge you in 2 ways:
Adding new languages
If you add a new language, Glotio will budget the number of characters to translate and after your approval and your payment, Glotio will do the translation quickly and efficiently.
Updating already translated languages
Every night Glotio checks if there is new content to translate (for more info read this How does Glotio update my translations?), it updates all your configured languages, you only care about the content in your default language. You can choose how you want to update the texts:
With manual updates, you pay when you want to update the texts pending translation.
In case of automatic updates, you can configure the monthly spending threshold not to be exceeded. At any time the budgeted expenditure exceeds this threshold, Glotio will send you a notice to decide what to do. If you exceed this limit, Glotio stops updating until you increase it.