The decryption cards will probably license for $10 to $20, much less than the $50 for a simple decoder or $500 for a full featured digital video recorder.
The server is used to control all of the infected victims with a targeted vulnerability exploit that can initialise the decryption process without the bad actor's knowledge.
Implemented correctly, this removes the usefulness of the decryption oracle, by preventing an attacker from gaining useful information that he does not already possess.
