ISBNs - to buy or not to buy when self-publsihing?

Hebrews12

Hi all. I'm looking to self-publish my first novel using KDP and I understand that you can use their free version of an ISBN but that will only allow you to sell on Amazon or you can buy your own ISBNs which means that you can sell anywhere but they're expensive to buy. I'm hoping that someone can help me understand which route I should go down please?

KDP seems to be the cheapest way to get my book printed. If I price my book at £7.99, by the time Amazon have taken off the printing costs and their cut, I'm probably making just over £1 per copy. So (and please excuse my ignorance) would I sell it elsewhere as surely this would involve getting copies printed (probably through KDP as they're the cheapest way) and then trying to get them into bookstores who would want a cut which would mean I'd be running at a loss. I can't help thinking that I'm missing something so any education in the simplest of terms would be massively appreciated please.

NanookOfTheNorth

I have no experience of book publishing, but a quick google search suggests £93 for a single ISBN

https://www.nielsenisbnstore.com/Home/ISBN

Does it then work out cheaper to print your own, but then you have the "hassle" of printing, managing the orders etc so depends what you want - obviously more than £1 the better