Oxford doesn't pay staff well unless you are in the top of the pyramid, i.e. a professor. Paradoxically those tend to contribute less to education. Senior postdocs and fellows do a significant amount of teaching but their salaries are incredibly low. You need to make lots of life compromises to be able to sustain yourself at one of those. For example, fellows teaching at different colleges often get stipends and salaries in the range of £30-35,000 per year. Keep in mind that those fellowships require a PhD and a stellar CV.

Most other British and EU universities suffer from the same issues. For more information, see this article at The Guardian, which generated lots of debate: https://www.theguardian.com/higher-education-network/2015/no.... In a nutshell the article states that "[...] I no longer believe that early-career positions at Oxbridge universities are viable for individuals without independent financial means." Also "[...] the median non-professorial academic salary at Oxbridge is £45,000."