Originally Posted by nux

So this is for a return flight?

The BA.com engine is trying to split a return fare and show the relative component for each segment when booking a return, and sometimes will give somewhat confusing/misleading results. In this case I think because the return LGW-NCE flights are cheaper it is showing a lower outbound price for the NCE-LON flights.

If you select the same outbound and inbound flights (NCE-LHR-NCE) it shows the same final price, it just splits the fare differently.

You can't buy the outbound for either price, what you are buying is a return fare in this case. The final price of the return is what matters.