i am so tempted to pull out my tazer (electric shock device) for that extra charge.
i usually tell them to stop the car and just move to another cab. with the crisis right now, taxis are literally lining up to get a passenger. heck, business is so bad they even try to ply you with chippy, chips and drinks that's conveniently hanging by the front seat head rest. beware of edibles though, you might end up waking in another part of the city, without your clothes and divested of your personal effects. and worse the taxi driver would have gotten his way with you (well, that's really not a bad prospect for some people i know)
in any case, make sure to check out the dashboard and if you see the rosary hanging by the rear view mirror, you can safely assume they are less likely to ask for that additional cost of transportation.
as for that other famous belief, unfortunately, it is true that riding a taxi in manila is the equivalent of a ride to hell. aieeeeeeeee...