JMich: Assuming I am to buy more games on GOG, the regional pricing of The Witcher 3 means I end up paying less for the same amount of games. If I'm only interested in one game on GOG, the store credit means nothing to me, so I do pay more for the same amount of games.
Yes, I acknowledge there are circumstances in the model where one can come out with an advantage. But as with my house analogy, these are exceptional cases rather than the normative. At least until such time where every item in every store is sold with a credit, and market prices and expectations are adjusted to compensate for that new trend.
People are using (and trading) the GOG credits, so they do have clear value. They are just not equivalent to a game that is already priced at the post-credit amount.
And I know you understand this, just spelling out my thoughts in general. :)
JMich: Edit: The numbers don't seem that proper to me, will have to recheck them. Idea remains though that if one buys more games from GOG, or even only from GOG, the store credit will translate to them paying the same amount for the same amount of games.
EDIT: Was posting while you were postscripting. Again, this is technically true, but the larger issue remains - the price is effectively the same only in this special case (more games are intended to be bought, specifically those which conform to the amount and terms of the credit). The general case remains that equivalency is not achieved across the board.