Looks like with some tinkering i figured it out. Trial and error for the win!
Heres what i came up with. Thoughts?
startValue = 16549376432298;
endValue = 16549396432298;
dur = 30; //seconds
s = "$" + Math.round(linear(time,0,dur,startValue,endValue));
s.substr(0,s.length-12) + "," + s.substr(-3,3)+ "," + s.substr(-3,3)+ "," + s.substr(-3,3)+ "," + s.substr(-3,3)