Yes definitely, with two parts to the justification:

(i) I otherwise paid I class fares and sometimes higher for Club World and Club Europe travel during the period, and for my four First sectors I probably would have paid the A class sale fares - the Avios saving is always calculated from the I class or A class sale fares that were available at the time of booking or the closest sale to booking and many of the Club World sectors originated in the middle east, where sub-GBP 2,500 fares are (were) easy to come by even at short notice

(ii) There were some Club Europe flights that came in at extremely high > GBP 1,000 fares - where this is the case I have calculated money saved from the appropriate I class fare, imagining that I took a Saturday night stay instead of flying Sunday-Friday.