I've heard this argument before - could you explain in more detail how you come to that conclusion?
From last years GERS report, Scotland's population is 8.3% of the UK as a whole, it raised 9.9% of taxes if you include a geographocal share of Oil revenue.
From the BBC:-
If oil revenues are included in GDP figures, Scotland is shown to generate more per head of population than the UK as a whole. For Scotland, it is £26,424 per head compared with £22,336 per head for the UK, according to Scottish government estimates.
If you do not include oil and gas revenues then there is little difference in the figures - GDP per head in Scotland was £20,571 in 2011 and for the UK it was £20,873.