There are a few optical storage mediums designed for long term archival storage. Like M-Disc or (as mentioned in the article) pioneers DM for Archive, both of which are still commercially available.

And provided they're stored properly, even more general consumer oriented optical media can easily last a few decades. Granted the environmental aspect of "proper storage" (<50% relative humidity, constant temp <80F and >50F) can be difficult to achieve at home in a lot of regions, but generally banks and credit unions have an option to get a safety deposit box which is generally in an environmentally controlled room. Other than that just store your media in an opaque single disc case.

I don't even know what to say about this mess, but yes: that's enterprise pricing. It doesn't need to be that way, but it can be because those are the kind of prices you can charge businesses. And really, just as a pleasant capitalistic side effect of this, is that the lower classes are completely locked off form this technology. It's not a mystery, it's not a conspiracy, it's business. And I hate it.

Tape is still the cheapest option for mass amounts of storage since the actual tapes are so cheap. You just need to store enough data to offset the cost of the drive. Drive cost increases very quickly the higher you go in storage density.

They used to be affordable. Nah ... they used to be cheap.

Recordable media isn't. Factory pressed media if stored correctly should outlast the person who bought it.