I can better that!!
I went to BA.com to book a J class return to SFO in October. I usually book a semi flex ticket so I can change for £150. I got an eye-watering quote for this fare (assume there is something going on in the city). Out of interest I checked the FIRST fare, which for semi-flex (i.e. £150 to change) was almost EIGHTEEN HUNDRED POUNDS less!
Lesson – its always worth checking all classes before confirming a booking!