Reading the annual accounts, they also mention the production costs of the Earthshot book, and the fact that over a thousand submissions were received by the date that nominations for the second year of the Prize closed in March 2022 - that’s going to require some expert time and costs to assess all the submissions and create shortlists for finalists (and they would have needed to done this for the 2021 awards also).
The accounts also show that only 1.7m was spent on Earthshot in the previous financial year, so it’s clear that there weren’t a lost of costs that were front-loaded, they all took place in the first year of the awards.
Obviously, you are not going to agree, but the £7.1m covers plenty more than just the awards ceremony and it seems it covered plenty of actual activities.