Well, believe it or not, the greasy take out joing, Five Faces, which is on Division between State and Dearborn, has an excellent falafel for just over $2! I absolutely love falafels and have had authentic falafels in the heart of Jerusalem....so believe me when i tell you that this falafel is that good. maybe not 100% authentic (use that white sauce that greeks use instead of tahini) but still very good.
one problem w/getting a falafel in america is that hte health codes forbid restaurants from making it a buffet style where you can keep walking up and adding more items (like hummos, more tahini, eggplant, tomatoes, etc etc etc) to your half eaten falafel.
anyway, stop through Five Faces some time and check it out.