Ha Ha the old EAN problem.
Yes it is an issue with amazon but I dont know where you have been looking but £100 per EAN code is silly. Yes you can register to generate your own codes which is quite expensive or you can buy unique codes of many sellers, Here is an example for a seller on eBay
https://shopgen.co.uk/out/ebay/UPC-EAN-Numbers-Barcodes-Bar-Code-Amazon-UK-EU-Lifetime-Guarantee-50--100000/143289725259
1,000 codes from these guys will cost you currently around £4
Hope that helps