There are 4 billion cell phone users worldwide. 500 million of 4 billion is just 12.5% of market share. This is wrongly assuming the "users" all own a phone. Still though. I believe Akumen is a Chinese brand. If they could somehow capture a large portion of that market then ... maybe not too silly.

Having said that though, if they thought they would sell the 500 million then they'd probably make even more.