To be fair, compared to the prices of Certum and other providers if you ever want to sign something for Windows, perhaps Apple isn't uniquely overpriced (they all seem to be that way): https://www.certum.eu/en/code-signing-certificates/
Looking more into the Windows side of things, I also found Azure Artifact Signing which is supposedly affordable at 8.54 EUR per month, but unfortunately they don't actually support individual users in the EU (only in US & Canada, meanwhile EU only gets support for organizations). I'd probably have to set up a SIA (equivalent of Ltd.) here first - it was in the plans for later, but this is a bit of a roadblock for using Azure too: https://azure.microsoft.com/en-us/products/artifact-signing
My tone might have been frustrated, but I will absolutely say that the code signing industry needs to have a Let's Encrypt moment of some description - at least commoditize it like Azure Artifact Signing was trying to do, but also for individual developers, across all platforms! Sadly, that doesn't seem to be possible when the platforms are intentionally walled gardens. I don't hate the idea of code signing, though - if done right, it's a good idea, same as TLS for (many) websites.