Its incredibly niave to think it costs Sony, co-developer of blu-ray, $10 to press a game onto a blu-ray disc. Its probably costs a dollar or less to manufacturer a disc by bow. They can sell blurray movies for $9.99 and still profit.
It will definitely be cheaper for Sony to stick with optical discs next gen if they don't drop the drive entirely.
That's pretty rare despite being constantly mentioned in this thread. I can think of a few that are strictly multiplayer games or the Master Chief Collection which is just a huge net installer disc.
Otherwise games still become gold and are playable start to finish off disc. Switch games on the other hand have quite a few that require a download.