Call Swiss, €2518
Book with CheapoAir, €2534
Call Lufthansa, €2541
Call Singapore €4759
Book With Expedia -- click through
Book With edreams -- gives a fare in the ballpark, €25++
I haven't called anyone yet because I hoped to book online. Agents aren't always on top of all fares, even when you give them detailed information.
BTW, AmEx Platinum Travel cited over 9000 USD for the same itinerary. Agent said she didn't know why...