Something's up. In Germany in a normal city I can get a döner the same size as the one in the photo for €3 ($3.50?). It's not sourdough nor high quality protein but that can't explain the $7.50 difference. Edit: as the commenter below reminded me, it's actually more like €4-5 but my point stands.
They're using over-the-top expensive premium ingredients, but if you just use regular supermarket ingredients, you could make a döner for far far less. Let me attempt a prices breakdown:
I'm in the U.S., and the nearby Aldi sells boneless, skinless chicken breasts for $2.49 per pound (a restaurant could probably order in bulk, and get that an even lower price). A pound is 453 grams. There's probably only 100 grams of meat in a döner. So 113g of chicken in a döner should cost around $0.50. (It cost them $2.50, a 5x premium.)
Pre-packaged pita bread (döner wrappers) probably cost far far less than $0.75. I'm not going to analyze, but I'm going to guess it actually costs closer to between $0.05 and $0.10. Then there's the sauce. It too, when bought it bulk, likely costs less than $0.10 per döner.
So that's all to say you can definitely make a good döner in the U.S. for less than $1 per döner in terms of ingredient costs.
In terms of labor cost -- if you pay someone $15/hour, and if they take 1 minute per döner, which is definitely possible if you do things assembly-style, then the labor cost is $0.25 per döner. If you're less efficient, then maybe the labor cost is $0.50 per döner.
So now labor + ingredients is somewhere between $1.25 to $1.50.
Lastly, there's rent/utilities/etc. This totally depends on where you're located, but assumeing you're in a non-super-expensive area, let's guesstimate it costs around $1 total per döner purchased to cover these things.
We've reached a final cost price of $2.50 per döner. I can see how a 3 euro price is totally achievable in Germany.
Food can be cheap in the U.S., even in nice neighborhoods. As an example, I offer "Tara Inn", a tiny old local restaurant in Port Jefferson, NY. (Their menu: https://zmenu.com/tara-inn-port-jefferson-online-menu/) They sell pretty darn good hamburgers for $1.00 each, cheeseburger for $1.50 a piece, a grilled chicken sandwich for $2.00, etc. And the food there is actually good. This, in a neighborhood (North Shore Long Island) where the typical family income is $100k+. (Although the immediate vicinity of Port Jefferson is not considered super-bougey by north shore folks.)
There's another reason why döners can be fairly expensive in the US (even at a places using non-premium ingredients). Turkish cuisine is still somewhat exotic here. The US doesn't have the huge fairly-recent immigrant Turkish population that Germany has, so döners fall under the realm of "exotic mediterranean" foods. Hence their higher-than-typical prices.