My view on this is that this is a very common practice arising from various observations and confusion in the our minds. This might have multiple etiologies ranging from basic concepts of cost minimization, availability of generic drugs and also a trade off of minor efficacy advantage for cheaper options.
This might have origin even to perception in the consumer's mind but in this full confusion, the only certain that that I can see is that a person only talk about the Direct Cost and not of indirect and intangibles!
Another way you can express the "high cost" you mention could be to analize if it is a catastrophic expenditure that the person incur in relation to the total household expenditure net from food expenditure; there are a lot of papers you can revise to check the way to estimate this equation.
Following the comment from Chistopher, this approach would be from the patient/household perspective.
the cost of medicine has a high share in the total expenditure on healthcare. it is roughly around 60-70 %. High cost are a real problem in developing countries where it can lead to catastrophic expenditure. the cost of drugs to the payer includes cost of drugs+ profit+marketing expenses, so the final cost is really high.