
It's widely known that Apple purchased PA Semi Conductor for $278 Million dollars. But what's not known is how much Apple had to sink into the company for R&D and licensing to get the A4 (and any derivatives) designed and out the door.
Mac Rumors talked to some experts in the field and did an article and suggests that the ballpark for that type of chip design from the ground up usually runs about $1 Billion dollars. That figure of course assumes you will get another fab to actually produce the chips... having to build your own fab and do your own production would at least triple that figure.
You can read the full article here: Apple's iPad Chip Development Cost Estimated in $1 Billion Range - Mac Rumors