What is the meaning of 'K' in 20K or 30K or 40K when disclosing price?
True. The letter is described to show '1000'. The prefix 'kilo' is derived from the Greek word chilioi or khilioi. Its short form was used for the metric system.
I still remember the first time I heard of 'K' used for 1000 other than kilogram or kilometer was when the 'Y2K' bug threatened the entire world! I was curious to know and discovered that it was 'Year 2000 bug'. Since then, using 'K' for a thousand (anything) hasn't been an uncommon usage.
Good read is here on a Math Forum
The SI prefix for a thousand is kilo-, officially abbreviated as k—for instance, prefixed to "metre" or its abbreviation m, kilometre or km signifies a thousand metres. As such, people occasionally represent the number in a non-standard notation by replacing the last three zeros of the general numeral with "k": for instance, 30k for 30,000.
Also, in computers K means 2**10 (two to the 10th power) = 1024. But in prices (or miles on car) it means 1000.