Calibre doesn’t natively support reading DRMed files, but there are anti-DRM plugins which are trivial to install. You need to provide a legitimate Kindle serial number for Amazon DRM, as it uses that to de-encrypt the files. When you add the file(s) to your library, the plugin automatically runs as a file conversion. It basically converts it from a DRM-locked .epub/.azw3 to a DRM-free .epub/.azw3 instead. Since Calibre already has file conversions built in, the plugin simply uses that existing system to spit out a DRM-free version of the same file, then it adds that to your library instead.
The shelves aren’t even empty. There are thousands of eggs in my local grocery stores. Every single store near me has eggs that are nearing expiration, which means people aren’t buying them. People are seeing the asinine prices, and opting to eat less eggs.
But the issue is that producers have realized they can blame the specter of inflation or supply chain issues to charge whatever the hell the want. Let’s say they charge $2 per carton, and can reliably sell five cartons at that price. Or they can charge $6 per carton, and reliably sell two cartons. With the latter example they make more money and pay less in shipping since they only had to ship 2/5 the stock. So why wouldn’t they just find an excuse to sell them at $6 per carton? That’s just economics 101.