you may have made 1.5 million but probably could have made 1.4 - 1.6 mil by selling the mats
I tend to agree with this. At least on my server, there is a large number of Biochems competing for the Exotech market. I can only move stims and adrenals quickly if I price them low enough that there is a pretty narrow profit margin.
Yet I can sell radioactive paste quickly.
Several people have found a good niche in Biochem that they can really move product on (e.g. sub implants), but I haven't been so lucky. On the other hand, all those Biochems need mats for their stuff so the demand stays pretty high for mats.