Hi, I wonder if some of the experts on this forum might be able to explain something strange to me?

I'm trying to book a flight from LHR-LAX, outbound Sunday 16th March, return Thursday 20th March. If I enter those dates on ba.com, I can get my outbound flight for £294 (economy) but the return flight comes in at what I consider a rather extortionate £1836, for economy at least! Total cost £2130.

However if I adjust my outbound date to Saturday 15th March (1 day earlier) and leave my return date unchanged, the return flights - literally the same flights on the same day - all drop to £398. Making a total trip cost of £728 if I take the cheapest outbound.

Why is it that by taking an outbound flight one day earlier and returning on the same flight, the total cost drops by over £1400?!

I've tried to 'cheat' by looking at one way tickets but the return leg on 20th March still comes out really expensive.

Can anyone enlighten me?

Thanks