Quoted from Patrunkenphat7:One HEP restored grail pin (in my case that’s either Twilight Zone or Indiana Jones Pinball Adventure) or 2 modern Sterns? You could probably get either 2 new pros or 2 used premiums.
I voted for the HEP, but I think your math may be a little optimistic on how much the HEP is going to cost. You need the donor game, to begin with, and a donor game TZ or IJ is going to be 5k(ish) minimum at current market costs (and the worse the condition is of the donor game the more the restore itself will cost). Then you have two ways of shipping at $500 or so each way. Then you have parts and labor, possibly needing a new playfield and almost assuredly needing a new cabinet.
HEP games are super expensive, the journey is a lot of fun though. Nothing beats watching an old heavily routed beater game turn into a better than NIB game. Chris documenting each of his restores is awesome and he cares about you having a good experience (which is awesome). If you go for HEP plan for the game being a lifetime keeper.