Back when I was waiting for my Roadster to arrive and I had more time to think (due to spending no time driving it), I worked out a rough cut at the amount of fuel that is used in moving the gliders by plane from London to SJC. This is a very loose estimate, so at best you should trust only the order of magnitude. In addition, I had to make a number of assumptions. I tried to make them in a way that overstated the impact of the trip, so I'll wind up with more of an upper bound than a correct result. In particular, I assumed that the plane makes the trip with a full fuel load, which is almost certainly not true since it's not all that close to its max range. I also assumed that flying the plane to its max range results in burning all of its fuel, which is wrong because there is always a pretty ample fuel reserve. I also assumed that the plane capcity would have been used if the Roadster hadn't taken it up. I used Wikipedia for my information source, with all of its attendant hazards. With those caveats, here is my math:
A Roadster weighs 2700 lbs, of which 900 lbs is the battery. If the rest of the powertrain is only 100 lbs (I'm sure it's more, since the motor alone is this heavy, not to mention the tranny and PEM), then the glider is 1700 lbs.
A 747-400 has max gross weight of 875 k lbs, of which 390 k lbs (= 220 k L max fuel capacity x 0.82 kg / L kerosene * 2.2 kg /lb) is fuel, and 394 k lbs is the empty weight of the plane, leaving a cargo capacity of 91 K lbs. Therefore, a Roadster glider is a little less than 2% of the capacity of a 747-400. The plane's max range is 7300 nm (nautical miles, not nanometers ), so if it uses all 220 k L of fuel it consumes about 30 L / nm. London to SJC is about 4700 nm, so the trip takes 141 k L of fuel. 2% of that is 2800 L, or about 800 gal of gasoline. A 30 mpg car would go 24,000 miles on that amount of fuel (assuming that jet A/kerosene and gasoline are equivalent).
So, even with my over estimations and giving gasoline cars credit for completely free transport, after a couple of years of driving the Roadster, you've make up for the plane flight.