If you already have an advanced account and you want even more, it's $1/month for an extra 100MB of space, $1/month for extra 200 MB bandwidth. Bulk discounts available.
Payments are made by logging in and clicking the upgrade button. Sorry, we don't accept checks or international wires yet.
If your site is nonprofit, cool or specially interesting, we'll probably give you as much additional features, bandwidth and space for free - please ask.