This question was raised in the ‘Want to maximise your product design? See how a custom ASIC can help?' webinar, view all the questions in the round-up blog post.
This is a typical trade-off when considering the specification of a product. From a CPU perspective, more performance typically results in larger silicon area and increased power. The impact on the cost of the product very much depends on the silicon technology and the size of the rest of the SoC – the increase in area due to CPU may be a relatively small proportion of the overall SoC.