Total cost of trip from Finchley to Heathrow for two people, using public transport: £35. (Two Travelcards, two tickets on the Heathrow Express)
Total cost of trip from Finchley to Heathrow for two people, using taxi: £40.
What you pay for that five pound saving: Journey takes twice as long and involves two line changes plus the drag between home and tube station, all involving heavy luggage.
So you’ll remember that next time, won’t you, loser? Shut up.