i remember paying 20c a game for a go on a brand new bally 33 years ago.
now to play it again and re-live my youth i have to fork out nearly 2k.wtf am i doing.

Ah yes, but if the market stays healthy, and you take good care of the pin, you can turn it around and hopefully sell it for at least what you paid for it.  And play umpteen games inbetween.  A pretty good deal!

Ballys (KISS, Paragon etc) cost around US$650 NIB in 1979.

I wondered how much a pin would have "sold for" back when they came out .... was thinking of creating the thread, but you've provided the budget.  $650 in 1979 dollars is about $3,100 in today's dollars (assuming annual inflation of 5%).  Of course if you bought a brand new one back when they came out, locked it up for 30+ years, it would be worth more.  Then again, that's long time storage, and they ain't as small as a diamond.