Files stored on your own server and delivered through our service would not count against your plan's maximum storage allocation on our server, so e.g. you could subscribe to our $18 plan or higher and have files totaling far more than 500MB. Some sellers may also prefer to manage their own files on their usual Web server via FTP rather than using the uploader in our Seller Admin.
Our Web caching system actually streams the file from your server first, and the buyer downloads their copy from our Web cache. The unique download link we issue to each buyer will cloak the "real" URL where your files are located on your server. Buyers have no way of even knowing their file did not actually originate on our own server and no way of bypassing our system to obtain your file directly from your server.
Also, we only stream the file from your server for the very first download of any given product's file; for subsequent downloads of the same product after that, we first check to see if your server's copy of the file is newer than our cached copy, and if not, then we simply issue the buyer a download directly from our cached copy. This ensures the best possible download performance for buyers while minimizing transfer bandwidth usage and charges for both of us.
After the buyer finishes checkout and the payment processor confirms the buyer's payment was good and completed, only then do we grant the buyer access to a thank-you page where we present their unique download link(s) automatically, and we also issue them a thank-you email with a link to reach the thank-you/download page in case they did not proceed to the download page after checkout. Their download link(s) expire after the number of attempts or hours (whichever comes first) that you specify in each product's settings.