Story

300GB for double sided, 3 layers a side. 50GB/layer So basically double the density per area of blueray.
If they can make as fast or cheap as the ancient LTO4 (800GB) tape, maybe we can talk. You can get an old drive for $500 and tapes for $20-25.
They'd have to be >$10 per disc for it to make sense.

LTO4 Tapes are about $0.032 / GB
Hardrives are about $0.045 /GB

I just go with harddrives and sell them and buy new ones annually since the price per GB keeps dropping.

Also I've been bitten by bad tapes and "archival media" before.

Sorry if my math is bad,
-sent from my iPhone while driving and eating barley soup. ;)