What does it mean?
Different people have different ideas about what’s valuable.
Where does it come from?
The earliest example I found in Google Books is in Hector Urquhart’s introduction to 1860s Popular Tales of the West Highlands:
Practical men may despise the tales, earnest men condemn them as lies, some even consider them wicked ; one refused to write any more for a whole estate ; my best friend says they are all ‘ blethers.’ But one man’s rubbish may be another’s treasure, and what is the standard of value in such a pursuit as this?”