Typically ecstasy is MDMA pressed in pill form together with an amphetamine, although as you noted MDMA is often changed out for some other 'research chemical' that is cheaper to source, and sometimes very dangerous.
Yet another obvious reason to legalize all recreational drugs...
'Typically' seems unlikely to me. I am not up to speed (no pun intended) on drug manufacturing/distribution, but years ago I wrote a psychopharmacology meta-study on the topic and most research I remember found that 'mixtures' or 'cuts' with two 'mainstream' active drugs were very uncommon due to increased costs and independent value. Most often, the active ingredient would be wholly substituted or mislabeled.
Perhaps that's changed, but it seems far more likely that cheaper substitutes would be used (ephedrine, 'research chemicals', etc).
Yet another obvious reason to legalize all recreational drugs...