Most expensive lake I fish is one of my home lakes. $15 permit, good for 6 months. There's a Summer Panfish/Catfish season, and a Winter Trout season. Trout season is about to close, need to spend another $15.
Next "most expensize lake" is a gorgeous little impoundment off in the hills. Limestone hills, water's fairly clear, small, great paddling lake. $10/year to fish, $10/year for a boat.