How many track days do you get from your brake pads?

I've done two track days and about 6 days of autocross and 5000 miles of street driving and my pads are half gone.

I'll replace the OEM pads next weekend in anticipation for my next track event in a couple of weeks. I'll keep the old pads to drive home on if I need to.

some questions:
Does autocross really accelerate your brake pad wear? I brake like a madman when autocrossing but it seems that you are only doing 6-10 runs per day so it shouldn't be that much additional wear.

I know racing type pads (Hawk Blues) will be better for stopping on the track but do they really last that much longer (as in # of track days before they need replacing)? And if I use an aggressive track pad, won't I replace my rotors more often?

How much should brake pads cost? I've been ordering the OEM ones online for about $110 for all four. What is a cheaper aftermarket pad that will give me the same or better track pad life and performance?