Real Music Entrance Themes Issues?

You're close with most of this. It's notoriously difficult to secure music rights for your productions unless you're a major film/tv studio without forking over an arm and a leg for usage, especially on a permanent basis. I myself have tried to secure music rights over the years for wrestling related material and even with friends in the music business have been unable to even get a response for some of what I was looking for.

It's likely some of the songs you heard in the past had rights secured for that live show and then released afterwards. Smaller companies either fork over some of the money or simply don't do it and hope they don't get caught (I've seen both done). But basically a label or rights holder can make a copyright claim at any time, especially with new media, for something that is used without their permission. It's just so hard to control and even now is still a bit like the wild west in terms of who uses what on the internet so you don't hear of it happening too often.

My favorite top-shelf examples are Eric Bischoff returning to Back in Black for one night and Hogan using Voodoo Child with 'Hulk Still Rules' happening. Bischoff reverted to a copycat WWE music library theme as it's pretty well documented Vince McMahon hates to pay for music rights. With Hulk, I am not really a Hogan fan personally but I wish he kept VooDoo Child forever because it was an evolution of his character (which is an almost impossible character to evolve) and sounds way better than his stupid, outdated and corny Real American theme. When he reverted back to that theme because Vince didn't want to pay for it, you can almost mark the moment he basically turned into a 'Legend' sideshow act. I'd go as far as to say TNA should have forked over the funds to use that theme during his run there, but why waste the money I guess if you're already in the hole.

I was a big fan of Europe's tunes, especially Final Countdown, in early high school before the song even made any sort of wrestling connection and I'm not shocked a hair band who has been mistaken since the 80's for having a song on the Rocky IV soundtrack and really only ever had one major radio hit in 'Carrie' asked for an absurd amount of money. They should basically have taken what they could get, but it's fine that they didn't.

Basically it boils down to 1. whether or not you can get ahold of the rights holders in the first place 2. how much those rights holders are willing to let you use it for (which in this case, 20 dates for 200k or whatever it was is absurd) and 3. how much you're willing to spend.

Supposedly Keith Lee’s music changed from NXT to Main Roster because the artist started making crazy demands to use it

That was the first thought that came to mind when the story came out that Final Countdown would cost an arm and a leg. I kept thinking didnt Geico just use this not that far back?