Output power vs idle power of an audio amplifier
It all depends on the power level where the amp transitions from Class A to Class B modes of operation, i.e. where the inactive transistor cuts off. 

There is a conflict between efficiency (transition to Class B at very low power, at the risk of some crossover distortion) and sound quality (high idle power, where the amplifier may remain in Class A up to 5 or 10W). 

Many of the "Class AB" amplifiers seen online are practically Class B and will show some crossover distortion as designed, as they are designed such that both output transistors are not "on" simultaneously. (Note that the Wikipedia description of Class B may be true for RF amplifiers but disagrees with 80 years of actual Class B audio amplifier design (p.49 of link)).

Some amplifiers allow adjusting the quiescent (idle) current via a pot - see RV24 on this schematic - after assembly and after replacing a transistor, you measure the output stage current and adjust the pot for 20mA (or other recommended figure). study the circuit for yours and see if this is possible.

TL/DR Your idle power is on the high side, but not unrealistic for a Class AB amp designed for higher quality. If it's adjustable it may simply be maladjusted, or "tweaked" in an attempt to reduce distortion.