I guess the real question here is what does cheap imply?
If you are viewing from a reasonable distance, something like a K mount 400mm F5.6 Manual Focus lens could do the trick. I have a vivitar MC 400/5.6 which i have seen go for about $100 in the last year or so (i bought mine new in 1982 for $159. as a stock close out) which provides good image quality. I could get reasnable infield shots during the 1985 ALCS from 400 feet away in the center field bleachers.
it also does reasonably as a wild life lens
if you don't need a zoom, for changing distance, then an old tele can work well