Ok i always use the same method on such passengers .
" How much it's the right price ? $1 less ? $2 less ? Or i can even give u a free trip , if u think u deserve it free . I can give cos i can afford , if giving you a free trip , u can grow fat , by all means , it's free for u ."
Usually it's women who give taxi drivers lots of problems , esp aged 35 - 50 years of age women ..... men will never do that .