well Engelhorn.. NOONE said it's a 100AH batpack ..
but a 550A motor can draw... well 550Amps obviously...
since you don't need that much if you're not going to use it.. it's fairly logical, that sometimes you indeed draw 550Amps from the batpack; at wich point a batpack with less than 100Ah is drained very quickly. (Ah / Amps gives you more than just a rough estimate

)
So yeah.. 100Ah for a 12minute full pull is the least I'd put on a kart able to draw 550Amps..
maybe that's just me though
Show me the 550A 144V motor for 500 and the controller for 200 then, please;
that'd be a steal and I can stack some away to sell them on ebay

Oh and those are very likely AC induction parts... not DC;
if you find ANY 72kW+ DC motor with 144Volts.. again.. let me know (I highly doubt that!)
Yeah.. they make their own motors and controllers.. that's why the exact same pancake motor and the exact same controller is on ebay every other week shipped from china for a few hundred bucks...
again I call BullsShirt (you know .. chicago... red with horns and such)
'sid