What’s wrong with this way of thinking?

“Economists argue that lower prices will result in fewer units being supplied. However, there are exceptions to this rule. For example, in 1972, a very simple ten-digit electronic calculator sold for $120.

By 2000, the price of the same type of calculator had declined to less than $5. Yet business firms produced and sold many more calculators in 2000 than they did in 1972. Lower prices did not result in less production or in a decline in the number of calculators supplied.”