We have been to the Food and Wine Festival 3 different times now and we love it. We plan our trips to the World to coincide with the Festival.
It is not extra, per se. There are many international booths set up all around World Showcase Lagoon. These booths sell sampler size portions of their native foods and they also sell either beer or wine native to their country.
The food samplings have cost $1 - $4 each in the past. We love to "Nosh around the world".
There are also many extra admission events that go on during the Festival. You can buy tickets in advance if you are interested in these.
Throughout each day there are also free beer/wine and even tea lectures held around the world you can enjoy.
They publish a Festival guide which is free and can be found all around the world. It has times and places listed for all of these events.
There is also the "Eat to the Beat" (I think this is the name) free concert series held during the festival at the American Garden Theatre. Each evening there are 3 free concerts, lasting about 30-45 minutes each. The performers are listed in advance, and are generally there 3 or days each. They are basically performers or groups from the 70's and 80's. For example, we say Chubby Checker one year and it was great fun.
We love the Food and Wine Festival and I hope you will too!