One of the most popular tactics of physical retailers (marking up a product and then putting it on sale for the original price), is starting to plague Steam.
Steam's frequent, massive sales, like the current Steam Summer Sale, are usually a cause for celebration for PC gamers looking to pick up games on their wishlists for cheap. However, the super sleuths over at reddit have noticed that quite a few publishers are taking advantage of the sale, utilizing an old retail trick known as the "pre-sale markup".
Essentially, what retailers (especially fashion retailers) would do, is take a product that normally sells for, say, $20. They would mark it up 100% to $40, and then immediately have a "50% off sale", during which the product is "on sale" for its regular price. It looks like Steam is no stranger to this, as Gaijin Entertainment, among others, have raised the price of their games only to discount them during the sale.
There's also some shady stuff going on with Rockstar and GTA V, in which the game appears to be on sale, but is only actually discounted when purchased together in a bundle that contains some in-game cash (essentially making the game "full price but with some free in-game cash").
The legality of this kind of tactic varies from country to county, but I think we can all agree that even if it is not illegal, it is still a dick move.
If you're interested in seeing which titles have changed price recently (in advance of the sale, specifically), be sure to check out the Steam Prices tracker.