A query regarding BJT Power Amplifier
To be strictly correct the power taken from the input source would be fair game for calculating efficiency however, most folk neglect that because a push-pull (for example) amplifier's signal input power is probably less than 1% of the output power. 

This is because a push-pull stage needs another transistor in front of it (usually common emitter) to set up the biasing for the push pull stage and if ten percent of the power to the push pull stage is provided by this transistor (via the power rails), then the input ac power to this front end transistor might be one tenth lower again and probably a lot more.

So, it's a fair point but a trivial one IMO.