Whatever they say it costs is a giant lie. The costs of future payments of socialized programs are almost never accurately accounted for.
The official debt is irrelevant. It's the fiscal gap, which everybody conveniently ignores. The government accounts for these costs differently so they don't include them in the official figures, but the debts are real things which will have to be funded with real money.
As of 2015, by the US government's own figures, the fiscal gap between projected government revenue and the present day value of all the services promised to its citizens (medicare, medicaid, social security, federal pensions, etc) is over 210 trillion dollars.
That's over 20X the official debt.
https://www.kotlikoff.net/sites/default/files/Kotlikoffbudgetcom2-25-2015.pdf
And it's the same case pretty much everywhere else, including the UK. All of these socialized programs are unsustainable in the long term. All of these countries that rely upon them will cripple themselves economically, and a lot of them are making it worse by also engaging in overseas hegemony. Warfare, welfare, and inflation. That's what kills countries.