Network transfer beyond your plan's included allowance is billed at $0.20/GB.
Most accounts never reach it. Measured usage across our plans runs at a small fraction of the included allowance, and the allowances were set so the cap sits well above normal use rather than just above it.
If you are planning something that will move a lot of data — a large migration, a media-heavy launch — tell us in advance and we will look at it with you rather than letting you find out on an invoice.