Depends what has been included in the project costs - if it meant registration of LNER as a trademark and various other things then it soon mounts up.
There will be all the posters up and down the network, the station signage etc. Now whilst posters would usually be updated at regular intervals, to do all on one day may have been bundled together into a 'one off' start up cost under the 'rebrand' heading.
To put some context - to vinyl wrap an average car or van is circa £ 1500. Assume that's a similar to the scale of what's being done for LNER on start up - you've got 31 x 91s = c £ 50k, approx 300 x Mk4 coaches = £ 450k, 30 x DVTs = £ 45k, 32 x HST power cars = £ 48k, 117 x Mk3 coaches £ 175k - Grand total of £ 768k just to do the vehicles.