"...based on a £40k salary..." How sad that it's still considered "normal" in London. So basically toys and noise are cheaper than hard cash. No wonder best devs go to finance.
Well, it seems thinking behind salaries at startups in London is simple - get a cheap workforce (ideally fresh uni graduates) and let them falsely believe that they can get rich by giving them a tiny slice of stock options. Ironically the people who are hiring them would very often badly struggle passing tech interview at another company - especially when sometimes you're interviewed by people who have no background in CS.