I'm wondering: what is the cost of such retention? If all intercepted data was encrypted, would that not eventually bankrupt the system? While such a wide use

I'm wondering: what is the cost of such retention? If all intercepted data was encrypted, would that not eventually bankrupt the system? While such a wide use of encryption seems unlikely, would it be possible to achieve the same effect by feeding the system with encrypted garbage? Even if it is eventually decrypted, it adds a lot of noise to the analysis effort, further increasing the cost.