Partly if not wholy due to the OP's reluctance or inability to tell us what is the whole point of this exercise, I'm not even sure if we're meant to be comparing comparing like-for-like single journeys, regular commute travel, or both. Because as well as single train journeys that are far higher than the car equivalent, long commutes can be far cheaper in a car too. I can't remember the exact figure or even provide proof that he is correct, but a colleague who commutes every day from Brighton to London mentioned recently his annual travel card including onward travel on the Tube/ buses costs him the best part of 7 grand.
The cost of parking in London is very high of course, but to anyone outside the Congestion Charge whose place of work provides staff parking, the fuel cost for modern fuel efficient petrol car for the year would certainly be shitloads less- probably around the 4k range for a car nearing 50 mpg for such journey. Add all additional wear/ residue costs per mile you can think of, it is still going to be much cheaper than seven blood grand.