About $2.55 / year [0][1][2], or, storing in AWS S3 "Infrequent access storage", about $180 after 5 years of recording [3][4].
[0]: https://www.amazon.com/dp/B00684XVFS/
[1]: https://wiki.xiph.org/Opus_Recommended_Settings#Recommended_...
[2]: https://www.wolframalpha.com/input/?i=0.027+USD%2FGB+*+24+Kb...
[3]: https://aws.amazon.com/s3/pricing/
[4]: https://www.wolframalpha.com/input/?i=(1%2F2)*(0.0125+USD%2F...