We will be booking a RTW early 2024 (for travel in 2025). I had originally planned to start in Oslo but was wondering whether I would be making a significant saving once I take into account an overnight stay in Oslo and return flights. There is also the convenience of starting our journey at our local airport (MAN). Can anyone give me an approximate difference for the following itinerary (DONE5) starting/finishing in either OSL or MAN?

(MAN or OSL)-DOH-NBO-DOH-PER-SYD-CHC-SYS-HKG-BOM-KUL-SIN-HND-LAX-JFK-DOH-(MAN or OSL)

Thanks...