Now do the math for the drones required to sweep the land for 200 cows, say, once a month.<p>A spare wheel probably costs as much as a magnet.<p>And don&#x27;t forget that the metal being ingested isn&#x27;t just sitting on the surface of the grass.  In many cases, it&#x27;s probably buried in the first 2 or 3 cm of topsoil and being turned up as the cattle uproot the grass.  Is your drone going to handle this?  Is it really handling all this at a price of sub-$20 per head over 10 years?  I&#x27;d have to see it to believe it.