I paid $6/litre for Avgas at Sabiha Gokcen (Istanbul) a few weeks ago!
Was that official, or some corrupt practice? That is the highest price I have ever heard of. Even Luxor HELX, where "corruption" was probably invented, is reportedly not that high.
I am planning on Istanbul this year, so I ought to do some due diligence, because by the time I am there, 600nm down from Slovakia, I won't have enough juice to go elsewhere...