Just for information - the first ISBN is $125 but that is because they also register you as a publisher. It's more economical to buy a batch of 10 for $295 which includes the benefits of one - I'm in the UK where we buy from Nielsen's but they certainly operate in that way, so you should be set up as a publisher as part of buying the 10 and it certainly implies that on their page -
https://www.myidentifiers.com/get-your-isbn-now - though you probably should just confirm that with them.