It all depends on how you look at it, but to consider its economics you may look at the following.
Dead weight of AAC blocks on structure compare to normal bricks.
Speed of construction and how fast you wish to build a project.
Workmanship and defect levels in executed work - smaller the size, higher can be defect level.
AAC blocks can be fixed with adhesive which does not require curing and normal bricks cant be done in that way till now unless the design of normal bricks is changed.
Wastage level and its utilization.
heat resistance
sound insulation
Environmental consideration
CO2 emission
natural resource wastage's
and there are many more factors which can be considered while calculating economics and factors are base on the need.