So far, sending files to your Kindle cost a flat fee — one dime per document for conversion and download over Whispernet. Looks like that honeymoon is over, as Amazon’s announced that as of May 4th, the Personal Document Service will be a variable fee of $0.15 per megabyte, rounding up. It’s still free of charge if you transfer the documents over via USB, and sending them to “name”@free.kindle.com will return converted files to your email address gratis

Original post:
Amazon to charge per megabyte to send personal documents OTA to your Kindle