To me, a toy camera is one made specifically for children. It can be cheap or expensive. On the other hand, my best friend had a "child's" 110 when she was young, and it was merely a shell around an average 110 camera.
I never considered a Polaroid a toy - just a different kind of camera for various different purposes. For example, my father was in real estate, and often used Polaroids to take pictures of houses for sale. Not fine photography, but not toying by any means.
I've an Holga, and while I'll call it my "toy" camera, I don't consider it a toy. It was cheap, so I bought it to see if I liked medium format; I still use it from time to time for it's unique qualities.