I think the point that people are trying to make here is that it really doesn't matter which is more expensive to produce, what matters is that heroin is definitely more expensive to produce than fillers- so a producer is losing money by not selling heroin as heroin, but instead using it as essentially a filler, because it does not have a significant effect on the user. If the producer has access to MDMA and heroin, why not sell MDMA and heroin and use fillers to bulk up the pills? It makes no logical sense to use heroin as a filler- especially because it wouldn't actually be enough to feel. So, thinking of it as losing money by not selling two different products, and thus not making twice the $$, yes the producer is preventing themselves from making more money than they could.
As far as I know, MDEA in pills has made people think that they had pills with heroin in them, when in fact there was none. Pretty sure I had MDEA once, it felt like a cross between being really, really stoned and rolling. I didn't move the whole night, I just laid there, it felt nice, but I can see how someone might suspect heroin- or some other opiate- was in such a pill if they weren't familiar with what else is out there.
Out of close to 2,000 pills tested by EcstasyData, only 2 have had heroin in them- that is 1/10 of a percent of pills. Assuming that ratio could hold up even for pills that haven't been tested, the likelihood of someone coming across a batch of such pills is slim (unless they are the ones making them)- and if they did, I doubt they'd even know it, since they wouldn't feel it.
