I think that there are limits to the usefulness of better BB's. In typical AEG's (sub 368FPS) the wind (by which I mean anything upwards of a good fart) and inadvertent shooter movement (by which I also mean deviation from perfectly horizontal in the X-Y plane) will affect accuracy far more than the difference between BB's of a minimum quality - I'd draw that line in the wallet at BB Kings with Bulldogs on the wrong side of it.
Blaster Devils are very good IME, but unnecessary for AEG's - ordinary Blasters get just as many hits in skirmish and it's only when shooting at targets such as the upper half of someone's face peeping through a 6" wide opening that the difference between Blasters and BB Kings comes into play.
At higher muzzle energies, where small differences will have much further range in which to affect trajectory, and particularly when shooting BASR's when single shots count far more than when firing semi-auto AEG's, yeah I think it's worth spending more, but not, it turns out, as much as £23-odd for 2000 Madbull 0.4g Tan BB's which do not live up to the hype...