I have mods installed, but nothing that adds new content other than wall lights, fridges, and the vents added by the replace stuff mod - was playing on unstable #4 at the time, and deep into lategame - I was at a point where all 7 of my colonists were fully bionic more or less - so about 5-600k wealth.
Considering the majority of the wealth value of the reward comes from the golden warhammers, maybe this is to do with them - as from the players standpoint they're only worth a fraction of their actual value.
Thanks for the info.