My brother studies Chemistry. One of the first things they told them was that they could make Meth (I think) with a street value of about 1000 times the cost of the materials, but the police would know where to start looking as soon as they got their hands on some, because it would be too pure, too well made.
Mind you, this was told to incoming (freshmen) students, presumably the professors would be able to make the precursors in such a way that the authorities wouldn't know.