Higher profits are nearly never the reason something costs more one way than it does the other. Free market economics pretty much takes care of that. The reason there is a higher price associated with a standalone battery and servos as opposed to getting them in a radio set is that it costs more to sell them that way. Each item has to be cataloged and inventoried, not to mention the space small items take up on the valuable retail shelves. And, of course, when comparing brands or even vendors, higher prices usually mean better quality or better service, usually both.