I'm trying to figure out how this works. And the website is deliciously vague about it...
First they give three options (breakfast, half and full) and then there are prices based on the hotel where you are staying. (standard, plus, premium and extra plus). And you can book 'extra plus' if you are staying in any hotel, but the
Disneyland hotel.
We do get the half board prices:
Standard: Santa Fe & Davy Crockett 55 EUR per adult
Plus: Cheyenne, Sequoia, NPB, Marvel 65 EUR per adult
Premium: Disneyland Hotel 125 EUR per adult
Extra Plus: all but Disneyland hotel, 150 GBP per adult.
The Auberge costs 95 EUR per adult.
So going from half board to Auberge might be (not taking into account that half board also includes your breakfast...)
Standard: 40 EUR per adult
Plus: 30 EUR per adult
Premium & Extra Plus: Include character meals.
However... You are already on full board, my guess is going to be less than 40 or 30 EUR depending on your hotel?
Not very helpful, but it might give you some guidelines.