I've read how expensive the LHR transport is...goes hand in hand I guess. Expensive to land at/transit through/get away from...yet I still wanna go there and check it out for sure.
I think my most expensive trip was JFK-EWR. I landed at JFK off of an overnight Cathay flight from YVR at about 5:30am or so. Asked the friendly transportation desk peeps what's the best/most cost effective way to get to EWR because my hotel was there as was my return flight. She said there's basically 3 options, 1) taxi but that's not cost effective 2) shuttlebus @ around $22 and decent speed 3) public transit which might take a bit longer but should be cheaper.
I'm adventurous and I wasn't in a hurry (other than I was tired) so I decided to try and be frugal and take transit. So it was JFK airtram (or whatever name it is) to New York Penn. I think that was like $12 or so, then it was a NJ transit to Newark airport station, another $10.50 or whatever.
In the end it cost me like .50 cents more to take transit and took a good 45-50 minutes more...learned my lesson. Whenever I'm in NY or that area now, it's the blue shuttle van I'll be choosing.