All the over priced "A" list titles. Paying over about $2500 for ANY pinball machine just doesn't make any sense when there are 100 or more great titles that can be purchased for under $2500.
I don't care who you are or what you like NO ONE can tell me buying a MM for $15,000 will give you 6 to 8 times the enjoyment of owning 6 to 8 "B" list titles.
Money guys driving up the price of a dozen or so "A" list titles don't make them worth the prices people are paying for them. Dollar per Dollar MOST "B & C" list titles are a better deal and will yield better return over the long run when you are ready to sell.