You have a point Eric, but in the case of Flake (and possibly Aero) it is a bit more complicated. The flake chocolate contains less fat, which, together with the structure, does give a different mouthfeel . In the case of Whisper, which also has air in it, there is a higher fat content, which also affects the mouthfeel. I think that in all the products containing air the ORIGINAL purpose was to get an effect on the eating quality. Because of the special production techniques and ingredient changes necessary, I doubt if there is a significant cost reduction in production. Far more important would be small reductions in the size of bars or number of units in the box/pack. These are , of course, nowadays pretty well publicised by the papers, though not the companies. I do remember a project about 15-20 years ago to produce a bar with less calories. This involved a combination of wafer (with much air) and aerated mousse in the centre, the thinnest layer of chocolate possible and a smaller bar (presumably thinking that people would not notice it was smaller). It was never introduced, mainly, I think, because it was pretty awful to eat (as are many "healthy " products)