hatberet

Except that most reputable universities don't let you do that. You can use your own textbook for the course, if you want, you just can't accept any royalties for it.

That might work at some universities, but there are a (not insignificant) number of students who simply refuse to buy used textbooks. After all, they aren't paying $20k per semester to learn old calculus!

The sad reality of the situation is that a professor's student evaluations (which do matter for things like tenure) will be negatively affected by the decision to use an old edition. Yes, sometimes it makes sense to tell an unprofitable/annoying customer to go away, but professors don't have that luxury in the university environment.

Edit: Curious why this is being down-voted. The truth hurts?

I'm not sure about Androids, but iPhones do not have a barometric pressure sensor, so the only way to obtain altitude data would be through GPS. For applications like this, where you don't need real-time altitude information, that low-power GPS paper from Microsoft could come in handy, but it's cheaper and lower power to just use a pressure transducer in the first place.

Ethanol has a lower density than gasoline. So, although it has a similar mass-specific energy content, the volume-specific energy content is lower. Ethanol has a greater resistance to ignition than gasoline. But, since consumers buy gasoline in grades based on the octane rating (usually (RON+MON)/2), you don't see any octane benefit in your tank and do get reduced energy content.

Well, I think part of the problem is the size of their market. How many more people do you think would buy Mach 6 spy planes if the cost could be reduced by a couple orders of magnitude? Government would buy a few more, but John Q. Public doesn't really have a need for a vehicle that can fly him to 100 kilofeet (even if it only costs a couple hundred grand). So, unlike the car business, where you expect to sell tens of thousands to hundreds of thousands of units per year, the best you can ever expect in the airplane business is a few hundred to a thousand over the total useful life of the model.

To further put this in perspective, Honda (not the biggest automobile manufacturer) sells almost as many Accords (not their most popular model) in just one month as total number of 172's (the most-produced civilian aircraft) that Cessna has ever sold in all of history. Note that the wikipedia page on this topic (http://en.wikipedia.org/wiki/List_of_most_produced_aircraft) is dominated by military aircraft produced for WWII, as well as pre- and immediatly-post-war civilian aircraft.

What this means is that you can't just hand-wave away the costs of building tooling (for making forged parts with complex shapes, for example) and optimizing the assembly line. Fixed, upfront costs do not get amortized to a near-zero per-unit cost they way they do with software and most consumer electronics. This is also part of the reason avionics prices always seem to be so badly out of step with consumer electronics: As an avionics manufacturer, the maximum theoretical size of your market is tens to hundreds of thousands, (there are on the order of half a million civilian airplanes in the world today) and your suppliers usually want you to go through a distributor for orders that size.

There was a company, named Eclipse, that recently tried to revolutionize the way aircraft are produced. Among other things, they badly mis-estimated the size of the Very Light Jet market (which they more-or-less invented) and failed to over-deliver (some would say they over-promised). Suppliers, creditors, customers, and investors got soaked, though the firm is apparently still a going concern. One data point doesn't make a trend, and Eclipse faced fairly daunting macroeconomic conditions, but the fact remains that the manufacturer using the most "modern" production techniques had to go through bankruptcy.

One final point: The aviation market also tends to be cyclical. Loans don't go away, but you can have your employees work fewer hours.

> It also means the Prius wins in a lot of states.

That's true. But I think Tesla is trying to sell the Model S to people who would otherwise buy a similar luxury car. There are a not-insignificant number of people in the world who just hate the Prius because it sacrifices handling, performance, and interior finish for the sake of fuel-efficiency. If Tesla builds and sells a car that those people like, isn't it still a net win? People who like hybrid Priuses can still buy them.

Tesla has a cute map of electricity generation by state: http://www.teslamotors.com/goelectric#electricity

It looks like there isn't any state where driving an electric actually produces more CO2 than driving a gas car. And that's before you include the CO2 generated from refining oil (which requires a fair amount of electricity).