£9,000 is about US$13,769 or so according to http://www.oanda.com . State universities in the US often have tuition and fees that are that amount or lower for their state residents. Of course, they receive subsidies from the state governments, much like Oxford receives subsidies from the UK government.
Living costs are not included in the above numbers. Oxford estimates £8,727 to £12,894 (US$13,351 to US$19,726) for the 9 month academic year, so the total is not too different from what state universities in the US cost for their state residents. (Of course, books and some other expenses need to be considered as well.)