They weighed it before leaving and Amy's bike, fully loaded (without water I think, but I'm not certain) was 25.5kg and Kyle's was nearly 27kg. So, 'quite a lot' really, whether or not that included liquid. They did appear to have a lot of duplication in their packing; two first aid kits for example, and proper Allen keys in addition to at least one multitool. Perhaps they'll shed some of this along the way !
This is their bike setup and weighing video:
View: https://www.youtube.com/watch?v=hJLRiszFMKY
And this is the kit video:
View: https://www.youtube.com/watch?v=vNeRRTR8i14