Your calculation is correct. I have another point to add to the
advantages. No need to worry about finding a parking lot.
However, there are other things to weigh. For example, taxis still
cannot beat the convenience of owning a car. Sometimes u just
cannot get a taxi by the road or even at the taxi stand. And even
if u call for taxi, there's still some waiting time involved, worse
if it's during peak hours.
And there are other factors like the irritating taxi driver, the
hell rider, the tortoise driver, the smoker driver, the high aircon
driver, the low aircon driver, the smelly taxi, the lost-the-way
driver, the purposely-lost-the-way driver, the overly-friendly
driver etc.
And for music lovers, you cant get to choose your favourite radio
station or listen to your favourite CD.