Now granted, I've done it Once for a family friend that needed an OS, but there's a couple things to know.
Firstly, unless you Want to customize some things (and one or two things I forget about), then you really don't Have to register the OS. It's also possible that you might be able to simply activate (and bind) a Win10 key to a new Win11 install. IDK if that's still going on or not, but I did it for my one rig and I'm pretty sure I've not paid for it in a VM, but I also may not have bothered to activate that since it's just testing.
Secondly, about those 'cheap' licenses. That's a bit of a tricky thing as some of these places you can get them are safe, some are not, but AFAIK, the way they're going about the licensing is still sketchy. I've read so many things about how some of these places are getting licenses via recycling (taking the OEM key from a dead PC and reselling it / probably not legal), some are abusing volume licensing (meaning that at some point it may not work again after say a reinstall), and then there's the straight key hacks. The last one can be in the form of a scammer getting into your computer, stealing all the keys and selling them. Often this is done during one of those calls people get 'from Microsoft'. If you ask Reddit, most don't care because it's cheap and the more legit places will apparently just replace a code that won't initially activate, but that makes me wonder if They're using a key generator TBH.