I have recently thought about burning some data to Blu-ray and therefore looked for some cheap blank discs. To my surprise, higher density Blu-rays seem to be much more expensive than lower density ones. In my country (Germany) for example, I could buy a 25 GB BD for 0,44€. A 100 GB BD would cost me 8,77€! At that price, it would be more efficient to store 100 GB on four 25 GB discs instead of one 100 GB disc (1,76€ vs. 8,77€). Sure, if it is one file I would have to split it first and combine it again when I want to access the data, but that effort seems to be worth it.
Why are high capacity Blu-rays so much more expensive, especially compared to HDDs or SSDs where the price per GB/TB usually drops with higher capacity?
BD-XL is a magneto-optic format, like DVD-RAM was. It requires dirrefent technology than pure optical BDs and hence the media are way more expensive.
Supposedly BD-XL last way longer and are used for archiving data.
BD-RE XL you mean. Sorta. It was/is much more like DVD-RW functionally than DVD-RAM.
DVD-RAM was truly trackless MO. You could format one with any HDD/SSD file system.
BD XL is the best consumer archival media out there. But it’s not cheap compared to stashing a few 18TB drives in different locations with a Faraday cage.