I wouldn't know my high as I don't play for points, when I play(..which is always online)  I style, I'm not the best although I can name the best IMO any day <.<(cough n3kr0.xT cough) but I'm still working on stuff, like for one I use special grinds too much....

And sometimes I tag *BLEEP*, still wanna get 51 in training >.< for those who don't know there is exactly 51 tags in training, and I've seen it done, I still can't get over 40 though.

Well my best THUG 2 combo is around 60 million, I find that If you seriously vary your tricks to a huge extent you'll end up getting much higher scores. If you want to get higher scores try using up your grind of a manual balances in one go at seperate times, thsi way you can keep you balance going for even longer. Also, when you get enough air, ALWAYS, do a double-button tap flip.
A tip for scoring points on flatground is that when you land onto a manual try tapping R2 so you do a pivot and turn 180 on your backtrucks, this is quite hard to get used to but it seriously boosts your points.