Trilarion: So, if there are games, whose value is even below 6$ (say 3$) and they would not be able to appear here because of high transaction costs, why not introducing a "low price transaction surplus" of 1$ for all shoppings below 5$. This way one could have a lot of these titles but people would probably buy them in bundles, making the whole process more efficient.

So one game for 3$ -> price 4$ (3+1)
Two games for 3$ each -> price 6$
One game for 6$ -> price 6$

Simple and efficient.

Another way might be to have a prepaid account (increasable in 10$ units, also giftable) and be able to pay from this account with some discount (say 10%) because cashflow and fixed costs is better for GOG with this model.