If people bought a meal like that for 1€ only, no one would be able to sell it. You couldn't make a living of it.
For 1€ you get a Hamburger from McDonalds. Even a cheeseburger costs about 1,30€ (or more) this time of the year (it was 1€ as well sometimes). For a pizza with medium size you usually pay at least 3,50€.
You get anything cheaper in Turkey, for sure. But you probably also get less payment? On the other hand the döner in Germany is for sure far better than that one in Turkey.