I think the reality is also that people think "dmd game" and put 90's pins in with games all the way up to spike, when the only thing they really have in common (for the most part) is that modes exist on them. My rule is generally this: the deeper the rules, the higher the price, when comparing similar games. Obviously lots of things factor in to that; do you care about visual mods/are you willing to pay for them? do you care what condition the exterior artwork is in? etc.
Maybe I'm the oddball, but I don't give a shit what the exterior artwork looks like save for the front of the machine. I care about the condition of the rails, lockdown bar and coin door more than what the sides look like. I'm also willing to pay more for mods, because I like my games to look good (inside the cab) as well as play good. I don't care how nice a game is on the outside if the inside has a rough pf and weak flippers with bare sideblades and a barren playfield.
I think everyone deep in this hobby would be happier if they followed the mantra of "it should leave nicer than it arrived" (and if they just accepted that things cost money, and nicer things cost more money, lol).