It's weirder than that though, as if you are paying someone (say) £35,000 a year for doing a job rather than (say) £21,000 in benefits that's an extra £10,080 in take home pay which is in the wider economy benefiting far more business than just related industries.
That's from just one extra job, scale that up and for every 1,000 people and that's an extra £1 million in the economy.
Whilst that's still tiny compared to the total size of the UK economy (£2.56 trillion), that's just the first time that moneys spent, as chances are it'll be used to pay for goods and services which will be used to pay other people who'll pay for other goods and services and so on.
You also set the mindset that there's jobs with doing so people aim to do well at school, rather than not bothering and potentially ending up involved in anti social behaviour, which further adds to the cost to the country.
That's before you consider health costs, which may include an unhealthy lifestyle, mental health issues associated with feelings of lack of worth, and the like, which could all be additional costs to the NHS.