I know airfares are difficult to explain but perhaps someone can offer an explanation to the following:
Multi city trip with three day layover in London going to South Africa (Johannesburg) for travel late June/early July 2018

LAX to LHR, three nights three nights in London, LHR to JNB, JNB to LAX - Virgin airfare is about $1300

JFK to LHR, three nights in London, LHR to JNB, JNB to JFK - Virgin airfare is about $1,700

How can the shorter flights from/to JFK cost $400 more than the longer flights from/to LAX???
Thanks

Fixing my typo!

I know airfares are difficult to explain but perhaps someone can offer an explanation to the following:
Multi city trip with three day layover in London going to South Africa (Johannesburg) for travel late June/early July 2018

LAX to LHR, three nights in London, LHR to JNB, JNB to LAX - Virgin airfare is about $1300

JFK to LHR, three nights in London, LHR to JNB, JNB to JFK - Virgin airfare is about $1,700

How can the shorter flights from/to JFK cost $400 more than the longer flights from/to LAX???
Thanks

In a word, capitalism. Laws of supply & demand.

That happens all the time. Heck, I've even seen situation where a connecting flight to a location is less expensive than a single leg from the connecting airport to the final destination - say LAX/JFK/LHR vs. JFK/LHR where the JFK/LHR leg for both itineraries is on the same plane.

It all depends on the popularity of the route, amount of competition from the given airport, time of flight, day of week, time of year and dozens of other variables. If someone had a system that would be able to guarantee you'd always get the lowest fare they could make a fortune selling it to the flying public.

I just booked return trips from a to b because the return was 30pc cheaper than the one way.
I used to book double return trips including both a Saturday or Sunday and it was cheaper than a return including weekdays only.
I would say that airlines maximise their profits. And it creates strange situations.

Thanks for sharing your various points of view. I have learned much from the discussion. Since there appeared no magic bullet I went ahead and booked the JFK flights and discovered Virgin Atlantic has child fares which saved several hundred dollars and made the price differential less dramatic! So now our family will gather at Heathrow in late June and three days later we will be on our way to South Africa. Thanks again.

Glad it worked out for you.

I would add only that airlines don't price routes based on their length, they price them according to an automated algorithm that reacts to changes in sales in real time, among many other factors.

I just had to book a flight from Charlotte to Washington DC for this Thursday due to a family emergency. Yes, it's a last minute trip on a holiday weekend - I know that, but it is costing me $520. Grrrrrrrr.