the prices represent extensive market exchanges typical of a market economy, not reciprocal exchanges typical of an economy based on reciprocity.
It seems likely that almost all farmers were aware of these prices. We do not have records from the most humble of farms, but even they do not seem to have been isolated householding cocoons. They were not fully autarchic, whatever their aims may have been. They paid taxes, they sold produce and bought items even though most of their
consumption was of home-grown food.
...ancient Rome had an economic system that was an enormous conglomeration of interdependent markets.
Temin is attacking the view of Karl Polanyi and others, which is that markets are a more modern phenomenon. For example, Rosenberg and Birdzell, in How the West Grew Rich, paint a picture of the medieval economy as one in which prices were set largely by custom, and trade accounts for very little economic activity.
I think that Temin goes too far in suggesting that we should view Rome as a conglomeration of interdependent markets. Most of his evidence appears to be records of prices. But it could be that prices were established largely for tax purposes, rather than for trading.
Land might have been freely traded. However, not enough surplus was produced above subsistence for trade in goods and services to have been a major economic activity.
For Discussion. What other evidence exists that supports or contradicts Temin's thesis?