These letters are a scam. They are relying on many people not knowing the details of their domain registration and simply forwarding the inflated renewal fee to them and in the process transferring the domain registration. Screw the letter up and throw it in the trash.
If you renew through DreamHost, the domain will remain registered at DreamHost and you will save money. I would not even contemplate renewing through the 'Domain Registry of America'. Like I said, throw the letter away and ignore any future correspondence from them.
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