Rag,
1. What evidence do you have to support the assertion that prices from other suppliers will be lower.

The EU subsidises its farmers and imposes tariffs on world food to protect them.
EU food is the most expensive in the world.

Cars from Japan and elsewhere compete very well with German and French products despite tariffs against them.

2. Yep, OTHER people are getting THEIR imports at lower costs, great for them. We however are paying MORE for our imports.

Currently the EU makes us impose taiffs on imports from outside. Brexit will end that.

3. What evidence is there to support the assertion that the EU will still need the extra 11 Billion with the UK withdrawing, their costs will decrease to some extent.

Huh? We are a net contributor by that amount! When we leave it stops!