Yeah, it was a bit of a mess getting all the paperwork done but when I was signing up for iBooks distribution back in ~2014, I secured a block of 10 easily, for free, as a Canadian publisher and could have received more with some evidence I'd need them. I expect it's up to the organization that administers the ISBN system in your country to set the price. ISBNs tend to vary by country: https://en.wikipedia.org/wiki/List_of_ISBN_identifier_groups
The FAQ of the company responsible for selling ISBNs in Germany (1000 ISBNs cost ~310 EUR incl. VAT here) states that the country of the publisher is the decisive factor on where to buy the ISBNs. So if a book written by the author got translated to German, would he have to buy a German ISBN?
Otherwise he could just acquire all his ISBNs in Canada for free?
