I'm in the maxing out stage of my Town Hall 8 village, which means I don't use elixir much, and I have full elixir storages all the time, with a capacity of 6,000,000 elixir (3 level 11 storages).
According to the wiki, level 11 elixir storages give 10% of their current resources when destroyed during an attack. There is a maximum cap for amount of elixir stolen from storages, which is 450,000 elixir.
However, most of the times when my village gets completely destroyed, 3-star raid, the amount of elixir stolen is only about 350,000. This is way less than the maximum cap or 10% of the resources, and I'm not even taking into account collectors, the Town Hall and the Clan Castle.
Why?
Best Answer
When a higher townhall level than you attacks you, they suffer a loot penalty. The current loot penalty is show in the following graph.
You can also find out more on how the loot you can get is calculated here under section "Loot".