This help page explains why sending Updates & Newsletters is an extra-cost service, rather than a standard feature included with a monthly subscription:
Updates are not available for remotely-hosted files because of the sudden spike in system load and other performance issues that would incur, above and beyond what it takes to serve Updates for an uploaded file. Our system handles Update download links exactly the same as regular paid download links, so with every download attempt, our system would first have to check your remote file URL to make sure our cached copy matches that and, if not, restream a fresh copy from your URL and then serve the file from our local cache, which would result in throttled download performance and a major hit to our local system until we have a copy of the file cached to our Amazon S3 provisions to start serving it from there. Uploaded files don't have those problems because we have a copy of the file synced to S3 within 15 minutes of the upload, so uploaded Updates would be served from S3 from the get-go. We're considering some possible solutions to these issues, so if that all pans out, we might be able to start allowing Updates for remotely-hosted files in the future.
That said, note that you can temporarily upgrade to a larger plan without actually paying the higher rate. When you upgrade to a larger plan, the change in account limits take effect almost immediately, but your first payment at the higher rate is deferred until your next monthly payment is due. It appears your next payment is due on the 21st, so as long as you delete the uploaded file and re-downgrade to your current plan before then, you won't wind up paying the higher rate at all.
We can also offer to delete all files you have uploaded to products that have a Remote Product File URL entered, so you could reclaim the storage space those files are using unnecessarily. To confirm your identity and attend to this, we would need you to email this request to Support along with your E-junkie account password, or your Subscription ID (from your Seller Admin > Account Summary screen), or your original activation code (from the original "Account information" email we sent you at registration):