Its a business district and so it can be cheaper but at weekends not weekdays, randomly selecting the Hilton in march is consistently circa £350/night of a weekday and £175 for a weekend whereas say the Southbank Hilton is more like £250 weekdays and £225 weekends but is much more variable

London is more blended in districts than some other cities and so the rules arent as hard and fast, certainly in recent years the areas like the City and Canary Wharf are vastly more busy at weekends than they used to be, both used to be a ghost town of a Sunday. They arent terrible places to stay but there is a definite premium in the week which I'd question the value of paying for if there isnt something you actively want to do in the area.