The PM salary is around £160k. If he resigns, his salary will go down to around £80k backbench MP salary.
If he had a better offer on the table, if someone was offering him jobs/consultancies he'd walk, but his brand is currently too toxic. In the circumstances, he can't afford/doesn't want a pay cut of around £80k pa pro-rata.
But I suspect it's not just about the salary, I suspect it's also about the other perks, the grace and favour accommodation and also not being able to play lord of the manor at Chequers any more.
He's apparently rented out his London home, so resigning and moving out of Number 10 will pose difficulties for him and his family.
As a London (well, Henley) MP he's not like other MPs who have a home in their constituency in the Home Counties or Yorkshire or wherever that he could move into.
I suspect he can't afford to move out. He's been so reliant for so long on Tory grandees/party donors funding his lifestyle, he lacks the means.
Boris Johnson and Carrie Symonds have taken out a buy-to-let mortgage on their townhouse in London, amid a row over the reported £200,000 refurbishment of their Downing Street flat
www.mirror.co.uk