Also you don't usually see newly released titles discounted less than a month later by 50%
Probably not as steep as 50% off, but if you factor in the bundles/perks some digital distro companies are offering, the savings is ballpark 40-50% or more off a combined purchased. For example:
Bioshock: Infinite Pre-order from Green Man Gaming included the following:
$15 Store Credit (Bioshock: I is now $45 to you).
X:Com Enemy Territories (going price at the time was $30, so assume $15 off to you if you resold the key, Bio is now $30 to you, bam 50% off already)
Copy of Bioshock 1 (not much, but a nice gift to someone you know, bam $5-10 saved, now BioI is $25 to you)
Copy of 1-game (from a list of 5), cost range from $20-30 at the time for some of the tittles (assume a flat resale value of $10, Bio: I to you is now $15).
Again, anyone paying console MSRP for new PC games is doing it wrong. With all these companies fighting for your dollar, now is the best time to be a PC gamer. Don't trust GMG? Amazon was running a similar deal except they gave you $20 credit towards any 2K Game, plus X:Com Enemy Territory + Bioshock1.
EDIT: Deals like the ones above just reinforce to me that digital sales are lucrative at even $10-15 dollar price points. There is no shipping involved, no warehouse storage, no store front, no overhead costs that retail sees. Even a giant like Amazon can still run such a good deal to compete with Steam/GMG/others - that tells me they did the math and they know the chance of selling a few thousand extra copies at ~$30-40 to them is still far more profitable than selling copies at $60.
As blackened said at the start of this thread, these companies don't do these sales as favors to consumers, they calculated the risk and most likely know the ROI is worth the offerings.