I wonder if something could be worked out like a rebate for giving up access to a title (e.g. 10% of current retail price or original sale price, whichever is less), or a discounted license transfer to a friend (perhaps the recipient pays 10% to the publisher to transfer the license).
That way, publishers still make money, friends can cheaply "give" games to their friends, and everyone else can still feel like they're "selling" old games, which would hopefully increase engagement in the platform. I know I have a ton of games I no longer care about, and if I could "sell" them, I would, which cleans up my library and makes me want to spend the balance.
Also, if a game is no longer supported by a publisher, transfers should be free.
I do not see a good reason why one should not be able to sell the game more expensive than the purchase price. Say when the title becomes unavailable from the original source or was obtained as part of a bundle.
That way, publishers still make money, friends can cheaply "give" games to their friends, and everyone else can still feel like they're "selling" old games, which would hopefully increase engagement in the platform. I know I have a ton of games I no longer care about, and if I could "sell" them, I would, which cleans up my library and makes me want to spend the balance.
Also, if a game is no longer supported by a publisher, transfers should be free.