At the time of the MIC's release, one of the things that the community pretty widely considered to be kind of an issue was that in a game with about a skrillion magic items, most slots had a clear winner, maybe one or two other interesting choices for certain characters, and then a vast sea of items that were apparently designed without the concept of "opportunity cost" in mind. They probably could have nerfed down the obvobvobv choices - almost all of which are included in the DMG - but instead they chose to try to make other choices more interesting. You could make an argument that the execution could have been better, but the intent seems noble to me.
3.5 never really came to a good general solution in terms of how to handle the fact that its core is deeply and profoundly unbalanced. (I don't think there is a good general solution.) Consider the most powerful elements of 3.5's core. If later material tries to present more reasonable substitutes - call this the Warmage Solution - you end up with options that are mostly novelties. For classes, this is a pretty okay solution because people are willing to use a less-powerful class for novelty or because they find the concept interesting. Magic items don't have as much personality as classes, though. If you take the too-powerful stuff in the core at face value, and introduce comparable or near-comparable substitutions later, you do produce interesting alternatives, but you also continue to persist the game's balance issues.
Now consider the less-powerful options in the core. You can take them at face value, and when producing potential substitutes later be careful not to obsolete anything. This is the Samurai solution. It produces stuff that doesn't invalidate even the poorest options, but just produces stuff that is itself a poor option. You can also write off the poorest options when producing potential substitutes for them, and put together something a little more competitive. Call this the Warblade solution. Its drawback is that it looks like power creep.
MIC leans heavily on the Warblade solution, with the "substitutes" for many poor items simply being new versions of the same item. If you consider the old Ring of Universal Energy Resistance to already be a "kick-ass magic item" (very few people do, and it's never ever ever considered one of the "big six"), then making it cheaper is significant power creep. If you don't, then it's simply making it more competitive with the obvobvobv items. In fact, after the big six, most magic item budget is spent on dealing with encumbrance (which is usually pretty cheap), mobility, avoiding action-denial effects and stat-drain, defense against various other nasty things that can happen to you, and class-specific or build-specific boosts. "Energy resistance" isn't in anybody's big six. I doubt it's in most people's big thirty. That said, if somebody actually considers the Ring of Universal Energy Resistance good, then yeah, making it cheaper is big power creep, but it's hard to call that anything like community consensus about the item.