To illustrate this point you can imagine the economy as a machine that takes energy and transfers it elsewhere. In a perfect world the energy that goes into the machine would equal the energy that goes out of the machine, however, we know that some of the energy is lost to things like friction.
In this analogy the transaction costs to trade are like the friction in the machine; the machine (or the economy) become less efficient.
While the Dark Web and other technological innovations can decrease the transaction costs they won't eliminate them entirely. Even still, I welcome these innovations and the decrease in economic friction that they bring with them.