Need an ISBN number for your self publishing project? Head over to the ISBN Application Form for the US. Bowker, is the name of the company with stewardship of the ISBN Agency in the U.S. they will process your application.
ISBN numbers are issued in blocks of 10 numbers, so the nice thing is that you can publish nine more books without registering for new ISBN numbers. However if you only want to publish one book, you have to pay for all ten.
As of this writing a block of 10 ISBN numbers costs $24.95 plus a $225.00 processing fee. Which means that the price of an ISBN number is about $25 each. If you require more than 10 ISBN numbers you can get them at a discount.
When you apply, you can also purchase bar codes for about $25 each.
Keep in mind however that many self publishing companies will sell you a single ISBN number, for instance LuLu will sell you a single ISBN, and a EAN Bar Code, and some distribution for $34.95.