The Jargon File (version 4.4.7, 29 Dec 2003):

smoke and mirrors
 n.

    Marketing deceptions. The term is mainstream in this general sense. Among
    hackers it's strongly associated with bogus demos and crocked benchmarks
    (see also MIPS, machoflops). ?They claim their new box cranks 50 MIPS
    for under $5000, but didn't specify the instruction mix ? sounds like smoke
    and mirrors to me.? The phrase, popularized by newspaper columnist Jimmy
    Breslin c.1975, has been said to derive from carnie slang for magic acts
    and ?freak show? displays that depend on trompe l'oeil effects, but also
    calls to mind the fierce Aztec god Tezcatlipoca (lit. ?Smoking Mirror?) for
    whom the hearts of huge numbers of human sacrificial victims were regularly
    cut out. Upon hearing about a rigged demo or yet another round of
    fantasy-based marketing promises, hackers often feel analogously
    disheartened. See also stealth manager.


The Free On-line Dictionary of Computing (30 December 2018):

smoke and mirrors

   Marketing deceptions.  The term is mainstream in this general
   sense.  Among hackers it's strongly associated with bogus
   demos and crocked benchmarks (see also MIPS,
   machoflops).  "They claim their new box cranks 50 MIPS for
   under $5000, but didn't specify the instruction mix - sounds
   like smoke and mirrors to me."  The phrase has been said to
   derive from carnie slang for magic acts and "freak show"
   displays that depend on "trompe l"oeil' effects, but also
   calls to mind the fierce Aztec god Tezcatlipoca (lit. "Smoking
   Mirror") for whom the hearts of huge numbers of human
   sacrificial victims were regularly cut out.  Upon hearing
   about a rigged demo or yet another round of fantasy-based
   marketing promises, hackers often feel analogously
   disheartened.