What the key is worth eh?
Definitely for FO:NV. The DLC is worth buying, and you'll never be able to buy it separately for anywhere near as little as that key is worth. ($6 at the very most, more likely $4-5)
19.99$ for the same thing. (And people are buying it too. It's the 68th best selling game on Steam right now)
The price of the Beth bundle ,27.32 evens out to about 2.5$ per game.
Even then, I think that if you think it's only worth ~4 or 5$ just because of a pricing error. That's absurd.
In that case, hey anyone got a Far Cry 3 key they'd sell me for 2.66$? (Since it was sold in a bundle for all 3 games for 8$ by gamestop with a pricing error last week)