ISBNs are confusing.
In many countries, they’re free. Apparently those folks have a God-given (or government-given) right to be listed as the publisher of their own work, finances notwithstanding.
In the US, you’ll pay for the privilege of appearing to have published your own book. Bowker owns the monopoly. Like most monopolies, they’re expensive. But at least they’re hard to deal with, too, so you get the full package.
Free ISBNs abound, if you’re willing to let the owner of the ISBN be listed as the publisher. I bought 10 ISBNs back when I cared. That’s the last money I’ll spend on them.
Let’s use CreateSpace as an example, prompted by a question on Linked In.