According to an article in the New York Times (in the business section) [Waste in Cancer Drugs Costs $3 Billion a Year, a Study Says]:
The federal Medicare program and private health insurers waste nearly $3 billion every year buying cancer medicines that are thrown out because many drug makers distribute the drugs only in vials that hold too much for most patients, a group of cancer researchers has found.
The study itself [Overspending driven by oversized single dose vials of cancer drugs, BMJ 2016 352:i788 doi:10.1136/bmj.i788 (Published 01 March 2016)] makes a stupid assumption: that the cost of the drug is linearly related to the amount of the drug. In reality, most of the cost of a cancer drug is profit, marketing, amortized development cost, and liability risk, which are independent of the quantity of drug in the vial. The price is driven more by the number of patients being billed than by the manufacturing cost of the drug, so changing the amount of wasted drug will have only a small effect on the cost.
Using a wild guess at the portion of the drug price that is due to manufacturing cost (10%) and the authors’ estimate of waste (10%), we get a savings of only 1% by the repackaging that the authors propose, and even that assumes that there is no extra cost to stocking different size vials when there are multiple different vial sizes for the same drug.
Changing the vial sizes so that nurses have to combine different sizes to get the correct dose is more likely to result in misdosing, which probably has a much higher cost than wasting small amounts of the drugs.