Quoted from Guinnesstime:
Because losing money sucks.
Pinball is the only “high-end” hobby I am aware of where the prevailing expectation seems to be to “have the cake and eat it too”! For example, no one in the audiophile or astronomy hobbies (where lots of stuff costs as much or more than a NIB pin and is equally frivolous in the grand scheme of things) expects to break even, let alone profit, from the sale of anything they bought NIB.
If you enjoyed the game while you owned it, then you really didn’t “lose” anything, you simply spent some money to have a good time! If you don’t see the “value” in this, then I’d respectfully suggest that you may end up chronically frustrated by pinball, because it is going to end up adding net stress to your life rather than being a fun, escapist, healthy means of enjoying life for a moment and RELIEVING stress.
(I don’t think I’d feel bad about selling Houdini for a $1000 “loss” after a year. My family and I would have had a year’s worth of fun playing the game and enjoying the aesthetic enhancements its design and lighting would bring to the room, easily worth the roughly $3/day.)