One of the primary reasons is that the pricing for invisible products is more difficult to evaluate. For example, a manufacturer can
determine how much it costs to make a DVD player, based on the
cost of the components and the labor to make it. Based on profit
margins, it is relatively straightforward to determine the cost of
the product to the distributor, who in turn can properly price it
for the consumer. Competitors can easily calculate those same
costs, and competition continually drives those prices down by
decreasing production costs and profit margins.