Hey,
sometimes (or always) it is cheaper to start a trip at an airport where your airline is not based and other airlines offer the same destinations...;
For example I flew from FRA via LHR to SFO with BA for 620 Euros beginning of April. Ticket is valid 12 months and rebooking for another returnflight date costs 50 Euro.
Another Example was last autum from CDG via ZRH to DXB with Swiss was half the price compared to a flight with same airline out of ZRH...
What I want to say is: check different airlines from different airports, maybe it is the best deal to go there with a low cost then and start there your trip..
Good luck!