you know that with munchkinry is the fact that in these kind of worlds everyone becomes pun-pun...Hell no. Those are common. You can go to Eternea (A city so big it takes up 7.5% of the known material plane), and buy those for a mere 90k.
Hell in Eternea there's a store called "Recette's" that if you're willing to shell out half a million gold pieces she has a Book of Exalted Deeds to sell you.
World 1 is VERY high magic, and also VERY high power gaming. Not to be rude to faerun and such, but their npcs would be second-rate in world 1, because in world one, research and tactics are a constant evolving thing. If someone find a way to do something easier or better than before, and she doesn't guard her secrets on how she did it, someone else will steal the idea and also do it.
For example the "Eternea eight" are an elite group of bodyguards that protect the young prince. Here's an example of what one of them is.
Dark Changling - Cleric 1/Rogue 2/Deathstalker 5/Rogue 2/Legacy Champion 20.
Ultimately giving her a death attack with a save DC in the 50-60 range. Plus she can death attack undead, and you have to make two saves against it.
It is VERY common to munchkin in this setting, because it is what would actually happen. "Oh you found a way to cast level 2 spells so early in your career. We should all do that it's a good idea". You wouldn't have someone who discovered something like be the only one who uses it, in the real world if a new technology is discovered it is quickly reverse engineered and stolen right? The same is with in my setting.