A market based economy assumes robust competition ... but a profit maximizing rich economy with a high concentration of economic power never has much effective competition.
In contrast a poor economy with disorganized ... haphazard ... supply, and with a multitude of individual buyers is a market economy, and the market efficiently reflects market equilibrium.
Many of the characteristics of a modern economy reduce competition:
Regulation makes it more difficult to have many different items in the market to do the same function ... and competition is reduced
Intellectual property sometimes gives a product a monopoly position ... whether or not it is justified
Branding makes the market ineffective ... an identical product that is unbranded does not compete as a similar product, but as something that is different. This diverts profit to the brand ... but does nothing to the inherent value of the product.