Well I find Kusadasi is Cheap however its a touristic place believe me its cheaper than some cities in Turkey !
As mickycoops said there is alo 24 , or bulbul which will cost you maximum 5 euro to have a good dinner with drinks inculuded if you want something light that would cost you probably 2-3 euro or something
if you like pizza there is a good Pizza place in kusadasi called PIZZA PIZZA KUSADASI which located oposite TANSAS shopping Center ( you will find Easily )
even they have a website so you can check th eprices and menus on net
PIZZA PIZZA KUSADASI MENUS AND PRICES http://www.pizzapizza.com.tr