When Shiga toxin is released from an E. coli O157:H7 bacterium, it can translocate to organs other than the digestive tract such as the kidneys and central nervous system (brain and spinal cord). This can cause hemolytic uremic syndrome (HUS) and/or thrombotic thrombocytopenic purpura (TTP) .
A strategy called dollar-cost averaging can help reduce risks surrounding an asset falling in price. The concept is straightforward - you invest a fixed amount of money in an asset once every fixed time period.
On the other hand, if you're interested in the average transaction price, then you might need: $$\frac{2\times 5+3\times 6+3\times 4}{2+3+3}=5 \text{ dollars.}$$. In your edited version, you say you want to evaluate worth, I think averages are not really useful. Totals would be more useful.