For the hosted fonts you pay a one-time fee for the font licence. If you stay within the allocated bandwidth limit (500MB per font per month), there will be no further costs for you. Additional bandwidth costs €0.001 per megabyte, per month.
For the self-hosted fonts, the one-time fee covers a perpetual license, giving you full control of your assets with no recurring payments. Font files are hosted on your own server, so there are no hosting charges.
