thank you for providing links and reminding everyone what the world was like before streaming
(Which also probably sets some ceiling on streaming prices and digital entertainment more broadly.)
It's also worth noting that a big contributor to the 90s spike was people replacing tapes/records with CDs, which were a far superior medium for most usage. The decline after 2000 was not streaming, since that didn't exist, but the wind-down of the upgrade cycle and the rise of file sharing and 0.99 digital track purchases in lieu of $15-20 album purchases.