On August 30th 2017, Retsos (19) was sold to Bayer Leverkusen from Olympiacos for €22 million, the most expensive fee ever paid for a Greek footballer.
http://www.ksta.de/image/28368190/2x1/940/470/e8ff40185c7c7b654e460ec4e3b4497c/Hr/b04-panagiotis-retsos-bucco-2.jpg
You are actually comparing a Holding/Defensive midfielder who barely goes up front to help score a goal in Siopis and Kourbelis, with an Attacking Midfielder and a Striker in Fortounis and Mitroglou? Bro. Many teams found it hard to break Panionios midfield domination. That's why they reached the playoffs.