I really think that it's kind of crazy that it costs less for a US student to go to university in the UK than in the US. Witness: a student who is going into a BA in history (starting in 2012) will pay the following:
Oxford University: £19,357/year (~$31,000/yr * 3 yrs/degree * 3%/yr inflation = ~$96,000)
Stanford University: $13,350/semester ($26,700/yr * 4 yrs/degree * 3%/yr inflation = ~$112,000)
New York University: $11,705/semester ($23,410/yr * 4 yrs/degree * 3%/yr inflation = ~$98,000)
UMich (Out-of-state): $18,794/semester (lower level); $20,121/semester (upper level) (~$158,000)
UMich (In-state): $6,220/semester (lower level); $7,023/semester (upper level) (~$54,000)
In these calculations, I assumed that there was only a 3% change in tuition cost year-by-year. Is this fair? Well, the average tuition costs have been rising at various rates, but many of them have been above 3%, so I'm going to say that it's a conservative estimate!
So... it is more expensive to send a student to a top-notch US university than the (arguably) #1 university in the UK (and the world). (Cost-of-living at Oxford is likely to be a little more expensive than at Stanford or UMich, though.)