I've found an official government review on smoking from 2022 (https://assets.publishing.service.gov.uk/media/62a0c3f38fa8f503921c159f/khan-review-making-smoking-obsolete.pdf)
Which has this info in it:
Annex F: the cost of tobacco to society
Figures on the cost to society have been provided...
It's not a simple task to work out the ultimate net effect as there are a lot of indirect consequences and also assumptions at play (for arguments on both sides).
It's possible to argue that smoking-related early deaths save the NHS money in the long term as treatments for other, unrelated...