First is the LCD. The cost isnt in the hardware, its in the dev time for them. I mean they look awesome for spectators, but for the player, you never see half the crap because who is paying that much attention to the screen while playing? Im concentrating more on the ball then on what sweet animation is playing.
Someone else said coin doors. This seems like a no brainer. Why do all the machines have coin mechs still and not blockoff plates? Easy way to save some on the BOM. If you need them, sell them at a reasonable price separately.
Most of the other stuff doesn't really add that much cost per machine. I mean say art for the playfield/plastics/sides/etc. Maybe you pay a one time fee or royalties if its an outside designer, but overall thats peanuts.
The only other thing, ands its actually possibly the most expensive thing, is the license. Im totally OK with the what Ill call "Grade B" license. For example, Deadpool is based on teh comics, not the movie. GREAT move. Its doesn't get dated as easily and you dont need things like the actual actor who did the movie. People all say they would do without a licensed theme, yet when any are announced, people are all over bashing it as a dumb idea (look at the deeproot thread for a lot of examples). I never by a machine on license alone, but a lot of people do. Also, the average person who isnt a pinhead will walk up to a big license and play it on location just because its that license. Not really true for unlicensed games. How well has Houdini, Octoberfest or Dialed In sold? If they were big licensed themes, even if the game sucked, people would buy it for that connection alone. Its smart business. Me, I dont care about license. Ill play Fish Tales, Whirlwind, Whitewater, Medieval Madness, Attack from Mars, etc all day long. You know why those are great games? They are fun.