(Sorry, didn't mean to post anonymously before - I am the 12:29 poster)
@phoenix, ChrisMiller, Paul4: absolutely, the transport system as we currently have it means that most people need a car to function. Therefore people tend to ignore the fixed costs (treating them as 'sunk' in economic terms), and a better public transport system is needed to change that. But the fact still is that running a car costs more than the marginal costs that people tend to consider when making the comparisons with public transport.
Transport on the continent (and further afield) does show what can be done with subsidies (and make no mistake, the low-priced fares you quote must be subsidised). But subsidies must be paid for somewhere. It is now acknowledged by transport professionals and politicians alike that for road pricing to work, the revenue must be hypothecated into public transport systems to provide a sensible system to the majority of people. If people then want to continue to have the comfort/luxury/convenience of driving on a route that is covered by an alternative, then it is not unreasonable for them to pay for the priviledge.
The aim is not to victimise driving - it will remain a necessary part of the transport system. But congestion is caused primarily by the wasted space of single-occupant vehicles, so schemes to encourage vehicle-sharing (whether private or public) are designed to improve the journey for everyone.
Trips to the supermarket are an interesting case - the growth of out of town shopping centres have fed the dependency on the car, and led to the demise of many town centres, which in turn people have little choice but to drive to the out-of-town centres. It's a vicious circle, and an example of poor foresight in urban planning.
We often want to have our cake and eat it. That's fine, but we've got to accept that it costs money.
Taxis in bus lanes? Yeah, tricky one. One idea is that they're considered a premium service for which a higher fare has been paid, so they should have the flexibility of service. Not completely convinced by this myself.
There are schemes in the States with lanes designated for 'high-occupancy vehicles', for which single occupants are now also permitted to use for a small charge. The idea being that you can use the less congested lane if its worth a dollar to you, and in doing so you've removed one car from the 'standard' lanes, so marginally improving the journey of everyone else as well.
Driving is generally accepted (academically) as being too cheap. We're basically not "paying" for all the costs associated with our journey. For example, the added congestion our journey makes on all other drivers; the noise pollution to residents along our route; the environmental damage.
And airlines versus railway costs? Well airlines benefit massively from cheap avaiation fuel due to international agreements. So there's no question that they're subsidised, even if indirectly.