Hello,
there is a sale for all Dishonored games separetely and in a bundle (3 in 1), but for some reason you can buy all three games for a cheaper price than buying them in a bundle. So I was wondering if there is some sort of a special content or something in a Complete Collection that is not present in separate games or maybe it is a mistake?

it is silly pricing

This is not uncommon. Owning all the individual parts will only have them push the "unowned" complete collection at you as something you'd like since you bought and played Dishonored.

I understand, thank you very much for your help Thank you very much for clarification

I'm seeing 4.08$ + 6.12$ + 6.12$ = 16.32$ versus 14.28$ for the Complete Collection.
If the prices are lower for you, maybe they applied regional pricing to the individual games but not the Complete Collection.

For me it shows $3.99 + $5.99 + $5.99 = $15.97 vs $15.99 for the Complete Collection.

Not sure why the Complete Collection is that much lower for Ice_mage. Strange regional pricing I guess.
.

According to IsThereAnyDeal, the US price is +14% compared to the reference price.