a fool and his money are soon parted
Definition from Wiktionary, the free dictionary
it is easy to get money from foolish people
- nobody ever went broke underestimating the intelligence of the American people
- there's a sucker born every minute
- Gregory Y. Titelman, Random House Dictionary of Popular Proverbs and Sayings, 1996, ISBN 0-679-44554-4, p. 103.