Just a point of clarification here: There are magic weapons other than swords in 0e, but swords are special. All magic swords (and only magic swords) in 0e are intelligent weapons.
Page 27: "Among magic weaponry swords alone possess certain human (and superhuman) attributes. Swords have alignment (Lawful, Neutral, or Chaotic), an Intelligence factor, and an egoism rating (as well as an optional determination of their origin/purpose)."
The fact that magic swords are the exclusive domain of fighters is supposed to be a major advantage for fighter characters. (Note: Supplement I allows thieves magic swords as well.)
Page 6: "All magical weaponry is usable by fighters, and this in itself is a big advantage."
This is what I was trying to say. The powerful stuff was Fighters-only, at least for a while.
You make an interesting point about whether a broken points value system (gold piece value being the points in the case of the 3e magic item system) is worse than no system at all. I've been finding with games like Champions, at least up to 4th edition, and M&M, that their balancing mechanisms are so borked as to be worse than useless. One is better off ignoring the point cost and just looking at the PC's capabilities.
I don't know, Champions has been around for almost 30 years and has been beaten on by stat-geeks probably more than D&D and most players seem to think it works just fine. Point-systems are abusable, sure, but after some public exposure and an edition or two they seem to work pretty well. Champions 4th is 20 years old so it may have changed somewhat for the better since then.
Otoh I feel that 1e AD&D ought to have had some sort of system for determining how many magic items the typical PC has at a given level. Gary spends a lot of time in 1e talking about how vital it is to avoid the Scylla and Charybdis of Killer DM-ing and Monty Haul-ism. Yet at no point does he give us a metric. At no point does he spell out how many PC deaths make a Killer DM (assuming average player skill) or what quantity of giveaway makes a Monty Haul DM. It seems to me rather pointless to talk about it at all if no metric is provided.
Monty-Haul is easy to spot in most cases, the Killer DM is more tied to player expectations IME. It was probably worth more discussion and it was - mostly in Dragon. As far as D&D I think more abstract guidelines actually work better than trying to make a mathematically precise system where the designer doesn't know the players nor does he know the situation. More precision = more likely to be broken as in my giant-slayer sword example. Something like "10th level characters might typically have 10 magic items. Fighters will have a weapon, armor, a shield or a backup weapon, a ring, 2 miscellaneous items, and 4 or 5 potions or scrolls." Something like that for 5th, 10th, 15th, and 20th has some value. Items have a lot of power relative to inherent character power in 1E/2E so anything detailed is going to be really really tricky. If we're about to invade the homebrew 9th level adventure Tomb of the Vampire King then a mace of disruption is a pretty big deal and makes the cleric a nastier fighter, possibly counting as a level or two higher than he really is. Next adventure is Against the Giants and now it's basically a +1 mace, kind of a crappy weapon against large creatures compared to even a +1 Longsword. That kind of variability is tough to account for in a system designed to balance overall combat capabilities.
Plus, assuming you do put a ton of work into figuring this out what is the benefit? Remember the mindset at the time of 1E was that we were trying to simulate a fantasy world in some respects. Areas of the countryside weren't necessarily zoned by level. Players were expected to know the difference between an ogre and a troll and whether they could take one on or not - running away was an acceptable response to "You see 2 trolls coming down the road." The idea that all encounters should be fair or balanced did not exist at the time. Rigorous analysis of the math was not going to happen because most players didn't care - it wasn't an aspect of the game that mattered to most players or DM's.
Now with 3E/4E there is some positioning of "balance" as a selling point - well now of course you have to do some work in that are because you're promising it on the box. I thought both CR and Item cost worked alright as a guideline with 3E, but you have to know your party and the situation or it's worse than useless - it gives a false sense of balance that's potentially going to wreck your game. The DM is the control mechanism that makes it work.
I've only recently started running 4E so I can't say a whole lot about it but setting all levels to the same scale - level 1 character is even with a level 1 monster and would typically have a level 1 item - certainly smooths out the granularity. Even there the situational variables can still make a big difference. For example, typed damage should be a part of the game but if the party is great at taking and dishing out fire & cold but runs into something with some variable resistances that dishes out toxic or necrotic damage then they are fighting at a lower level than what's on the label and it could get tricky. Items and powers both play a part there and in some ways that part is no different than the older versions of the game - you still need to know your players and their characters to really keep an eye on things.