I can cheerfully say that I like Diet Coke better than Diet Pepsi without someone saying 'Yeah, but you could always get Diet Ginger Ale'I'm comparing these two items - one clearly better than the other in every way possible, and 3 levels lower, and saying that I dislike that the item system works that way. I also don't like that there are items that give +2 to two skills that are 7th and 8th level, only difference being the skills, or +2 basic damage with melee is 2nd, ranged is 3rd... these choices seem random and arbitrary by and large, rather than a precise plan. I'm okay with fuzzy levels such that you don't have stupidness like 'So, 2000g for True Strike always on, right?' but I still want 'So if I want a +2 diplomacy item, it'll be the same as the +2 perception one, right?'
Well, of course there's going to be differences in levels of items that *seem* to do the same thing. Bracers of the Perfect Shot are perfect for Wizards who have Magic Missile, and Warlocks. They both have a *power* that counts as a basic ranged attack. Bracers of Mighty Striking are really only going to see use on someone who expects to take a lot of attacks of opportunity. There are no powers which count as basic attacks. The limited number of times you'll use the Mighty Striking vs the Perfect Shot, the cost difference works out.
The same holds true of skills. How often will the players make Perception checks vs Diplomacy? "Make a diplomacy check to see if you notice something." It's not gonna happen. (That if it's a 'diplomatic' situation, you'd use insight to notice something...). Perception is a *very* heavily used skill. Even in a heavy RPing campaign where diplomacy is used more frequently than normal, Perception will probably still beat it out.
The whole thing is a supply and demand economy. Players are more likely to want a Perception boost, so the merchants sell those items for more. If you find that your players pass up items that you think should be "obvious" decisions because they're cheaper than something that does "the same thing", adjust the prices/levels. Find out what things are worth to the characters. That's how economies work.