Quoted from hollywood:
Pez...What about shakers? PoTD mod?
I might be better off stripping and selling mods separate?
Mods are always a crap shoot. And their value is going to vary from buyer to buyer. Here's my personal take though:
At the top of the pile for mods that actually add value are things like shakers and ColorDMDs. True upgrades for the machine, that people will commonly want to buy themselves. You'll rarely get the full back out of them, but you can usually recoup the bulk. Saves the buyer money and install, it's a good deal for both parties.
Next I'd include mods that "belong" to the machine. So for instance the dancing boogie and skull pile on Scared Stiff. Those return things to the machine that should have been there and generally carry more real value. POTD mod, maybe? Cannon on AC/DC maybe? The line gets blurry.
When it comes to decals and LEDs and that kind of stuff, you're basically out of luck IMHO. Maybe the buyer loves what you did and will pay a little more because they'd rather have your machine than walk away, but aesthetics are such a personal thing. I'm probably going to rip out your LEDs to fix them, it's not a value upgrade to me. If you did a really nice job though I'm going to think about the time and money saved and at least factor that in.
Then there are mods where if you don't remove them I'm going to ask you to lower the price, because they're just so terrible.