Here's a question European leaders are asking themselves in the days after Brexit. How much punishment is my country willing to absorb in order to dissuade other countries from following Britain out of the EU?
Most EU countries do substantial trade with the U.K., trade that is now at-risk. Continuing that trade on advantageous terms will make Brexit look do-able to other countries. Dissuading others from following the Brexit path requires punishing Britain. However, punishing Britain also hurts their own national economies.
It is truly a dilemma. What makes sense geopolitically makes no sense economically.