Gents,
I rent and fly out to the Chicago area frequently. The Landing fees are not much more than $10 or $20 for GA aircraft at most airports and FBO's (Fixed-based Operators) almost always waived it if fuel is purchased. However, In a jet the landing fees vary from type and size; so its more expensive to fly a jet into any of the airports in the area. But the reasons for a lot of the GA aircraft not present at large class B airports like KORD are FBO services and FAA ATC clearance requirements. Even under VFR, a GA pilot must operate with the same protocal as on an IFR flight plan with the same time, communication, and clearance restrictions at a class B airport like KORD. Most GA pilots like to do things without too many restrictions and there is a lot of hassle when going into a big place like KORD in a GA aircraft.
Anyway, non of this applies to FS but just FYI...