This assumes that the virtual realities are constructed in a proprietary model with consumers and producers. Actually, everybody would have to be both, otherwise the system would grind to a halt with consumers unable to raise funds to purchase products.
But information doesn't need to be rationed in that way: what happens if people join an open source virtual reality instead, where consumption is unlimited and production is voluntary? Nothing in this world would be part of the economy as economists measure it.
I believe the "dismissal" is this cogent argument:
Shuffling bits around takes energy; if your virtual reality services grow exponentially and energy production doesn't, then the price of energy must also increase exponentially or else one of your VR companies could buy all the energy and shut down the competition.
Energy production (and computation) are limited by the capacity of the earth to vent heat into space at a reasonable surface temperature.
So unless you allow for an exponentially expanding real-world physical economy, you can't have an exponentially growing virtual economy.
The price of energy is capped at the cost to privately produce it for yourself, which is probably pretty low in the scheme of all encompassing virtual real estate fiscal gods.
