With Current Technology
It is not possible to have liquid oxygen bleach with enzymes. The hydrogen peroxide basically "kills" off the later, resulting in very short shelf life for that part of the equation. To get round this some offerings come as "dual" action bottles where one side is the oxygen bleach, the other enzyme based stain fighters. One squeezes the container to push each out at the same time, once they "meet",they can come together and each do it's bit to remove whatever.
You also have the latest "dual offerings" from P&G in the form of "Tide" and "Ariel" stain pacs. These are pretty much as above, but in smaller containers.
As for the price of Ariel in the USA, well the dollar is shrinking against the Euro, so importing anyting from Europe isn't going to be cheap. Consider also shipping anything out of Germany never is inexpensive.
Probably the best deal anyone can get is if they are in military or have acess to someone who is, and therefore can use their shipping service for things going state-side.
Being as all this may, $12.99 is not that dear considering you will probably use much less per wash than what is on the bottle. Very few places in the United States have water as hard as what one finds in many parts of the UK/EU, so even the dosage for "Soft" on detergent containers can be cut by 1/3 to 1/2. Much will depend upon load size, soil levels and other factors, but still...