$125 for one ISBN is only "very expensive" when you consider that ten ISBNs is $250. There are plenty of people who are willing to sell you an extra ISBN for cheap.
That said, $125 for an ISBN is only "very expensive" in a country where the average person spends less than $125 for a bag of groceries. Which ain't this one.
On a broader level, one of most baffling things to me has been how little people are willing to invest in their own futures. They'll spend $1,500 on an HDTV, but spend $125 for an ISBN -- when publishing their novel is presumably one of their lifelong dreams -- hell no! I can't afford it! It's so much money! I've listened to long harangues from musicians about how unjust the music industry is, and it turns out all they need is $2,500 to put out an album that's already been written AND recorded. I just can't understand it -- if it's that important to you, if this is what you really want to do with your life, why wouldn't you just put $2,500 on your credit card and damn the consequences? Honestly, I've made my living as a writer for well over a decade now, so I know what it's like to make no money at all ... but $2,500 is such an inconsequential amount of funds to spend on your own dreams that I just can't comprehend anybody complaining about it. In this society, $2,500 is the kind of money you don't even need to ask somebody for ... just fill out a form, they'll send you a card, and you can get a $2,500 loan -- or more -- without ever looking a human in the eye. So ... we're bitching about $250 now? No wait... we're apparently bitching about $125?