I wouldn’t be surprised if it’s already 10 Euros in some places. E.g. my town is notorious for not having cheap options, every single place has good meat, not only are none trying to get away with selling Hackfleischspieß as Döner, none of them use any ground meat at all (by law, a Döner skewer can’t contain stabilisers which severely limits the amount of ground meat you can include before it falls apart).
Eight Euros are pretty much standard here. Just under 10 if you want a Lahmacun Döner, and my town isn’t the poshest, by far – we just have good taste in Döner and one very old shop which always made their own skewers, own spice mix, own everything, which set the standard.
Try to get the same stuff in Westerland and I wouldn’t be surprise if it costs 15 Euros.