Google has made waves with its tests of Self-driving cars, which look like future mode of transport. Even though it is a still long way off, but automakers are getting closer and closer to that day.

Google has made stunning progress on the self-driving car project it launched two years ago.

In the recent report, it has been announced that Google self-driving car is fleet of cars and a dozen or so can come on the road at any time. It had logged 300,000 miles.

It's even started for testing in real-world conditions. An employee must still sit in the driver's seat and be ready to take control of the car. And California's Senate approved a bill to legalize this car in home state. But despite that progress, a true self-driving car is far from hitting the market.

That's because, according to a well-informed startup founder working on similar technology, the massive array of sensors Google has to install in its cars alone costs $250,000 or more.

Add that to the $45,000 retail price of the Lexus RX450h cars it's modifying, add in some other custom components, and you get a car that costs more than $300,000.

It makes Google will not disclose the cost of its self-driving car project, or any of its other far-out research and development efforts, a spokesperson told us. It has always characterized self-driving cars as a small side bet.

And it's true: Even if Google is spending millions of dollars-at least $3.6 million just on its current fleet of cars, never mind the engineering salaries that's a drop in the bucket compared to its overall revenues.

But if Google intends to take this technology to the mainstream, as seems to be its ambition, it must reduce the cost of its sensors.

And on the other hand, other major automakers are also experimenting with Self-driving Car.