According to the original paper, they needed a 17 Tesla magnet to lift a 10 g mouse. I'm not exactly sure how to extrapolate that, but if it's linear it seems like you would need on the order of 100 kiloTelsa to lift a 150 lb person.
And 100 kilotesla is much greater than the largest magnet ever created -- the cost of building a magnet of increasing strength increases exponentially. The most powerful continuous magnetic field is 45T and the lab has 300 employees.
I'm quite sure it's not linear by weight supported.
The field exists in the entire area, each water molecule gets supported individually by the field. So the field needs to be strong enough to lift a single water molecule against earths gravity. (Plus some extra since water is also lifting misc other stuff in the body.)
You don't need a stronger field, you need one that covers the entire area, at the original strength. To do that you do need it somewhat stronger due to the dropoff by distance from the magnet.
But you don't need it stronger to support the weight.
Magnetic fields drop off as the cube of the distance, because the molecules further away will experience much less force you will need a much larger magnet anyway.
That's not 'somewhat' stronger, that's a lot stronger.
If a mouse is 25 mm high and you would want to levitate something the size of a human of say 1.75 m high with the same density as a mouse then the required magnet would have to be roughly (8^6)/2 times as strong for the same effect.
Then you still have to take into account the size difference at the base of the field, figure another factor of about 10 or so for that.
If you take the 'easier' approach and levitate a person while laying down (probably a wise thing) then the required magnet strength would be smaller, but still not that much smaller, you now have a vastly large surface area to work with ~40 times as large, (30,000 square cm opposed to 75 square cm), and the height is still 10 times as much so figure another 8^3 as much for that.
