If uploads can gather vast new resources by Dysoning the sun using current or near future technology, this calls into question Robin's model that standard current economic assumptions can be extended to an uploads world.

So far as I can see, you haven't demonstrated this or even made an argument to this end yet. It seems to me that basic economics still applies if there is a dyson sphere. There would still be scarce resources, the direction of the slope of the supply and demand curves wouldn't change, etc.