A failed suite was brought against pokemon in 1999. [http://www.nytimes.com/1999/09/24/nyregion/suit-claims-pokem...]
- They're available instantly in effectively unlimited quantity, as many as you want to buy.
- Although technically there are many gradations, the quality label of an item ("Factory new", "battle-scarred", etc.) is incontrovertible and easily verified.
- As a digital good, liquidation is extremely low-friction and virtually risk-free. In fact:
- You can click a button from within the game itself to see the current market value in USD -- sorry, in "Steam credit" -- and another to immediately offer the item for sale at that price.
- Maybe most relevant to this thread, even without liquidating they can be easily used as currency to participate in unregulated online roulette, slots, sports betting and more.
So, yeah, there are some differences.
[0]https://www.g2a.com/call-of-duty-modern-warfare-2-steam-cd-k... ($7.23 USD vs Steam price of $19.99 USD)
[1]https://www.g2a.com/mass-effect-trilogy-origin-cd-key-global... ($13.66 for all 3 Mass Effect games or $34.99 on Steam)
The keys on those sites are generally sourced from physical copies in cheaper regions (as mentioned in a sibling comment), cheaply sold bundles (Humble Indie Bundle, and other similar sites), and other such sources.
You could possibly make an argument for gift-copies of games[0] being resalable, or games that can be added to third party systems (ME2 gives a CD key that can be added to Origin, for example) though the latter would be limited to one attempt per-game per-account.
[0]http://www.g2play.net/category/24773/factorio-steam-gift/