Apparently, LUL pays £1,300 a go for a Track Retrieval Device.
That might sound quite reasonable if it were actually a 'device' in the popular understanding of the word. But it is a stick with a sticky pad on the end. Hence its usual moniker among station staff - the 'sticky stick'.
Private companies which make stuff like this must think that LUL is run by a bunch of suckers who will put their hands deep into their corporate pockets for any simple gadget they can come up with.