I'm not sure why it pisses anyone off...
Everything goes on sale eventually. Things going on sale before they're even released is pretty damn special ed, but that's another issue entirely.
When something is new, it does indeed have a higher value, and any wishful thinking on the part of a particular game designer doesn't change that. It may not have a higher value to a particular individual, but people are not logical so even an entirely offline experience is going to be valued at a higher level when it's new. This would hold true even if games stopped progressing visually, other mediums of entertainment that do not suffer from advancing technology so quickly decay in price just as fast. For a primarily online game, new is the only time it's a worthwhile purchase for most people. Your online community will almost certainly die out within months, to a small fraction of it's original size. That early community is what many people are interested in, the large, diverse player base, with which to match themselves against. Once it peters out, they move onto the next. A six month old game holds no interest to them at all unless it's one of the rare few that hold a massive community long term.
What we're seeing is the changing industry allowing games to simply exist in perpetuity. When they were purely a thing of retail, the stores dumped their stock, either to a warehouse, or in a bargain bin, once they got tired of the last few copies taking up shelf space, and they were rarely seen again. Perhaps when they came back up on peoples radar, they were actually worth more than originally sold because of the scarcity of the product. Once you remove concerns of scarcity and shelf space at retail, by providing them "forever" via direct download services, they should follow the natural curve purely based on demand.
Game companies might should be charging much higher prices at release, from a profit maximizing perspective. It would be interesting to see just how many people simply couldn't wait and would pay a hundred bucks, knowing a game would cost half that a month after release. There is a risk that such behavior would turn gamers off of course, and that newness factor might result in far fewer sales a month in than there would have been originally, but the natural progression down the demand curve requires a steadily shrinking price to get all those people who weren't interested in the product at it's original price, but are at half.
Price reductions are also good for the early adopters as well. Sins of a Solar Empire probably doesn't have even a dozen people still playing regularly that bought it originally. Out of hundreds of thousands of people, the community of active players is probably only a couple thousand. Most of the mods wouldn't exist, the online community would have completely dried up years ago.
That said, I actually like the early adopter plans, but that's because I'm someone that buys things early on specifically to reward companies, so I'll benefit from it. Giving stuff away to the people who can't wait, and are the primary driver of such add-on sales, is potentially a really stupid idea. It will require the loyalty buys, like mine, outweigh the can't wait buys that would have gone to the DLC anyway.