kursk wasn't just about physical losses of men and armored vehicles, it was about concentration and consumption of irreplaceable resources; namely all of the striking power of the german army was concentrated in two small places whilst the russians didn't have to weaken other fronts to amass their superior striking power in those places
I don't have numbers handy but Soviets also concentrated most of their best forces around Kursk (I think something like 70% of their tank forces) as well. They could afford to because Kursk was an obvious target and they knew Germans plan to attack there and Germans could only strike at one area. Soviets did "weaken" other parts of the front, but as I said they could.