Why 5 ore? :)
This ore issue has been ongoing since the Chaos patch, and there's still no clear explanation for it.
2500 gold is quite enough.
In the Chaos patch, it was only given in the first version as 2500+5 ore (so that you could at least build a Citadel and not waste a construction day if you didn't find resources in the first few days).
Afterwards, it became just 2500.