A film telephoto lens will be about 80 - 200mm most commonly (I also have a 75-205), and you'd be using the 200+ portion if you want to bring in the image of wildlife from afar. I found this to be adequate for most shots. See my album on here for my chipmunk photo - this was @ 205mm of my Vivitar 75-205 f3.8 manual lens. I bought that lens used from a local store for under $200 in the 80's.
When I found this to be not enough, I add a 2x teleconverter, so this gave me in effect 410mm. The image darkens a bit but you do get the shot.
A recently inherited from a friend who passed away a Vivitar 500mm mirror lens, but I haven't used it yet. But I was with him when he bought it, and in the 80's it cost him about $300 new. They come up in the used market every now and then and compared with much more expensive prime lenses of the same focal length, it has its drawbacks, but most times, in bright outdoor light he got an acceptable image.
Higher than that, and then things start to get pricey..
Hope it helps!