The 135mm prime is the cheapest good lens in the used market and has been for thirty years. Every SLR system made one, most made several, they were sold in enormous numbers as portrait lenses, and then autofocus arrived and the entire installed base became unwanted. A clean M42 Takumar 135 or a Canon FD 135 costs less than a decent filter. On a crop body it becomes roughly a 200mm equivalent, and that is the focal length where industrial subjects start behaving properly.