External flash: cheap 30$ flash vs expensive 300$ flash, what's the difference?

It will still give good flash and about close to the same correct? So i just buy this cheap one?

this is a cheap 30$ flash for any DSLR cmaera
http://www.ebay.com/...0495310607

For $30 the flash is fully manual and probably with a low guide number.

$300 flash units are usually dedicated to work with a specific camera system. These flash units are fully automatic and will shut off, once enough light has reached the sensor

It is possible to get a decent flash unit for much less than $300, but this is not one of them. This is junk… Of the cheapest sort. Many claims made in the ad, but no substance. No guide number specified, none of the normal info you get about a flash.

I'd guess a guide number of 40 feet or so, which is actually pretty pathetic. To be useful, even more so if you want to bounce the flash, you need a guide number of at least 100 feet, and more is better.

If you want decent but cheap, look at the Yongnuo flashes. Not much more for the base model, $40-$45 or so, but they work. They are completely manual, no auto anything units, but perfectly good if you take a little while to learn how to use them.

Usually the cheaper, 3rd party flashes have a shorter life - sometimes very short.

And they are usually not as powerful.

And they typically don't have the full range of functionality as the $300 version does.

Like anything else, you get what you pay for.