As a consequence, BOGO feels like a better deal than one item at 50% off MSRP. A 50% discount is a change in the asking price; the value of this item must have depreciated in some way for the seller to want to get rid of it (e.g., this garment is going out of season), and the price I'm paying is a fair deal that I'm happy to accept because I don't need to indulge in extravagances.
But in a BOGO deal, the asking price hasn't moved (or, as the article discusses, may actually be inflated); the fact that I paid full price means that it retains its original value, and the one they throw in is simply an enticement. In other words, I purchased an extravagance at full price, but it was a deal because I walked out with two. The amount paid is double the previous example's, but the perceived value is fourfold.
This isn't even getting into the actual value of perceived value (cf. the sticker price of wine vs. its perceived quality). Really interesting stuff.