on steam USA site version the price is $7.99 while UK version is £5.57 plus VAT. So i look around and it does need to be 20% VAT: https://www.gov.uk/vat-rates
And it keep leading back to this: https://www.theverge.com/2019/4/5/18296527/european-commission-valve-antitrust-o...
So yes Valve is breaking the law by making games cheaper at other countrys, something the developer might not be aware of or unable to do anything.