I think the most expensive would be flights booked with Codeshare connections. I found the following EWR-Cairo

Continental Airlines USD 9184.00 J1E

I think the most expensive Continental metal flight is EWR-Hong Kong at around 8k.

I tried to price out Newark to South Africa (Since flying EWR-Amsterdam-Cape Town is SO far), even though Continental says it is serviced with a codeshare it's not pricing out. Should be around 9-10k...