Cool. If you can prove this, buy the $599 ticket and file a low fare guarantee request; UA will give you $100 (
http://www.united.com/CMS/en-US/prod...guarantee.aspx ).
But … when I do a one-way search for a 12/30 EWR-LAS flight I see a $226 option. It looks like you are showing us the round-trip price but you have only shown us that the itinerary is identical on the outbound portion.
I bet that round trips are $599 for 4 pax or $535 for 1 pax, with a T fare on the outbound in both cases and with different fares on the return portion (inventory may be 1,2, or 3 in the cheaper bucket). Can you show us the full trip and fare solution you've found?