I agree that they can be, the one I linked is homemade from lentils and rice and the gluten free version does not contain anything exotic and the only expensive thing is a small amount of mushrooms.
This recipe is for black bean and sweet potato burgers but I used it as filling in enchiladas and dh(another meat lover) has actually requested a repeat.
http://onceamonthmom.com/sweet-potato-black-bean-burgers/