I have a feeling that data is wrong. If it's accurate it's definitely been pushed up by huge outliers on the top end (like £50+M properties in Chelsea and west ken that are zone 2)

I think the median zone 2 terraced house is more like £1m, can't find a statistic but I just bought a £1.5m house in hackney and there were 10 £1-1.3m properties for every £1.7m+

Still, a £1.3m house isn't completely infeasible in London :-).