Cool I get that, they are worried that they will send the wrong message to the gamers, the problem is that message is ALREADY out there so too late boys and girls. Also, that article is a bit old and sort of out of place, GMG, GG and other are already doing the same thing.
Also, whatever your approach to Sales is, if they are good or bad for the industry understand this, an average gamer has a limited budget to spend for games every year. Which means, if every one kept their prices at 100% (and at times devs overprice their games) that said gamer has a very difficult choice. The more discounts there are, the more an average gamer like me will buy.
Also, discounts, especially the heavy ones, in my opinion are EXTREMELY important because they make piracy absolutely NOT worth the effort and keep in mind, a lot of people download games simply because they can't afford yet another 50 Euros for some over priced and hyped game(im not saying that downloading games of torrents is good, its not).
Buying at Sales allowed me to expand my library of games to some more less 300 titles, wihout discounts I would have about 30-40 games simply because I couldn't afford them.
Mind another thing, Indie games are already taking a lot of the market and they don't charge 50 Euros, but often offer an extremely long and fun gameplay (for example: Defender's Quest, Kingdom Rush, Legend of Grimrock, Fieldrunners and many many more). Big companies won't be able to compete with them if they over price their games.
Now tell me this, I want to buy Blood and Blood 2 games, in the pack they were in I would have to spend to much money and am completely not interested in other games included in that pack, while they are at 50% im just not convinced, im on a limited budget and there is a ton of other games I also want to buy. If those two games were on 75% sale I would insta buy them, along with some other if they were 75%, because im always looking at how much fun im getting for a given price.
I doubt I will buy games at 50% at GoG this Sale, there is most likely a lot of people who will do the same. Question is, would you rather me buy 0 games at 50% discount or say a dozen of games at 75%? (to be honest I have like 40+ games on my wishlist would be hard to even begin to decide which ones to buy)
One thing is clear to me, no one cares if i buy those games from GoG or not, nor do I care from whom I buy my games, as long as it is the best deal for me, just trying to point GoG's attention to this.