steam
I am debating whether or not to get the Potato Sack (yes, I realize I've been debating for several weeks now) bundle through steam.
I already own: Defense Grid: The Awakening, Super Meat Boy, and Audiosurf, all of which are part of the sack pack. What happens if I buy the Potato Sack?
Do I get 2nd copies of the three above mentioned games to gift elsewhere?
Is the price of the bundle reduced by the games I already have?
Do I get nothing special for already owning those 3 games?
I agree with corroded that you should just give them the key, but to answer your question:
If you purchase a copy of a game you already own, you may or may not receive a giftable copy to give to someone else. According to Valve, the only cases where you get a giftable copy are:
Users who own Left 4 Dead and then go on to purchase "Left 4 Dead + Left 4 Dead 2 Bundle" will receive an extra copy of "Left 4 Dead"
Users who own Half-Life 2 and go on to purchase “The Orange Box” or the "Valve Complete Pack" will receive an extra copy of “Half-Life 2”.
Users who own Half-Life 2: Episode One and then go on to purchase the "Half-Life 2: Episode Pack”, “Valve Complete Pack” or “The Orange Box” will receive an extra copy of “Half-Life 2: Episode One”.
Users who own Dawn of War II and then go on to purchase "Dawn of War II Gold Edition" will receive an extra copy of "Dawn of War II"
Users who purchase the available four packs for specific Steam titles will receive three extra copies of that title to gift to friends.
Extra copies may apply as a part of some limited time promotions. In that case, information on what will be included with your purchase will be listed on the storefront's transaction page.
When trying to activating a Game you already own (or a bundle you already own parts of), Steam will warn you in a popup which game/parts won't be added to your library. You then have the choice to cancel the activation.
Per the Steam article on the subject
Extra copies are not given in most cases.
Only titles purchased in special promotions as outlined below are eligible for giftable extra copies
There has also been some discussion in gaming chat about the ethics of giving away extra humble bundle keys, as the site says the keys are for your sole use.
The original discussion was here. Ullallulloo emailed Humble Bundle support and asked for us. He posted the reply in chat here. Here's what it said:
"Our Steam keys do not generate giftable copies on Steam. Please consider your bundle a "unit" and not to share copies of the games or Steam keys from it.
If you'd like to give a copy of the games away, we have a system in place that allows you to buy a gift key from www.humblebundle.com so your friends can have access to direct downloads as well as any Steam or other keys we have included.
Please let me know if there's anything else I can help you with.
Thank you for your support"
For non-Humble Bundle trading, I would suggest the meta post related to game trading.
Best Answer
As of March 2016, Steam now subtracts the price of owned games from bundles, so you don't have to re-buy them.
In fact, here's a bundle viewed from my own account:
And from incognito:
Note how the base price of the bundle is about $5 cheaper when I'm logged in.
Packages
However, it's important to note that Steam makes a distinction between "bundles" and "packages".
With packages, the prices are fixed, and you pay the full price no matter what. So it would be silly to buy the game and then buy the game + OST package. Because you'd be paying for the game twice and only getting one copy.
Before buying the game:
And after:
That base price won't budge.
...I just bought a game to illustrate a point.