To get 1000 coins it took me 36 110 seconds = 10.0305556 hours. So it seems that getting one coin takes you approximately 36.11 seconds. I've gotten to level 22 this time. Hope this shines some light into things, but remeber that all of these values aren't exact due to obvious reasons.
I hate those stupid speed hackers. Pisses me off after all the time I put in and they suddenly advance to 3rd or 4th place, pushing me down another spot :\