NEVER use building queue, as it will cost you
I was experimenting with something else when I came to this find. It exists for DL, DA, and TA.
Using building queue costs a lot more BCs than choosing what to build one by one manually.
You can test for yourself easily.
Start with one game of any type, choose any race, then start game. Immediately set total spending and social spending to 100%, this way, no other things like research will mess with our BC expenditure. Now save. Queue up three buildings, any buidlings, and hit end turn until they are all done. Note the remaining treasury. Now load the savegame, build the first building, when it is finished, build the second, and the third. They finish at the same game time. And you have the same building results. Now look at the remaining treasury. Comparing to the first try, see the difference?