Don't go crazy replacing stuff that isn't broken with hundreds (or thousands) of dollars worth of parts.
Don't be ignorant of machines value vs. condition and allow yourself to be ripped off by some of the shadier sellers out there; check a sellers rep; the time it takes can save you plenty of heartache.
I don't think many people are "stuck" with Pins they can't sell. At a low enough price I will buy anything, even if I am out of room. Kinda like houses, you can lose a whole lot of money on them, but if every house in my town went down to 10 bucks I would buy them all. Since someone else would do the same all the houses in the town are not dropping that low (exceptions can happen... I guess parts of Detroit?).
Anyways, it is a hobby. Expect to lose money, especially buying NIB.
Games like Transformers LE and Avengers LE are not $7K games (when you compare what you get with other used games), even with a fake LE sticker and even with people paying NIB prices in that range.
It is okay to have fun, pay whatever and live life. Just be honest with yourself. It is a hobby. Hobbies usually cost some money. Compared to other big boy toy hobbies pinball is actually pretty cheap unless you go cookoo for coco puffs crazy.