Anyone able to help calculate what I can expect to pay with companion voucher for new booking. They have initially said it'll be another 2,000 Avios + a few hundred quid each. Has gone off to fares, but in my impatience if anybody smarter than me (or that has a voucher) can work it out please ?

2X Pax

Original Booking
125,000 Avios
LHR-LAX CW
LAX - LHR CW
£1750 Cash (Although my e-ticket receipt says £2,550!)

New Booking
LHR-SAN F
LAX - LHR CW

Receipt attached - not sure why the cash amount is more than what I thought.