"Individuals can own and sell property" is part of but not the whole concept of free market.
All the economic theory of free market (and all the advantages of it) rely on a few core assumptions, like liberty to trade and set prices, but also lots of buyers, lots of sellers, full competition, low barriers of entry and full information.
Just as it's well known that a market that devolves into monopoly or oligopoly does not work like a free market anymore, or in the case of severely unequal bargaining power, the same applies in the case of information asymmetry, which also is well known to lead to a failure of free market.
So whether "people are easily affected by suggestion" does matter, because if that becomes the case and companies are widely using effective methods to do so, then the resulting economic structure of the competition is not like a free market.
All the economic theory of free market (and all the advantages of it) rely on a few core assumptions, like liberty to trade and set prices, but also lots of buyers, lots of sellers, full competition, low barriers of entry and full information.
Just as it's well known that a market that devolves into monopoly or oligopoly does not work like a free market anymore, or in the case of severely unequal bargaining power, the same applies in the case of information asymmetry, which also is well known to lead to a failure of free market.
So whether "people are easily affected by suggestion" does matter, because if that becomes the case and companies are widely using effective methods to do so, then the resulting economic structure of the competition is not like a free market.