I’ve always figured that base set holos are of equal rarity from booster packs. Putting aside Machamp (for obvious reasons) and the three starters (due to popularity), this seems to be generally borne out in the PSA population report for 1st edition base set. However, I am wondering why this is the case when Gyarados, Hitmonchan, Mewtwo, and Ninetales were also available in theme decks. I would think these holos would be more commonly found, but that doesn’t seem to be the case with PSA-graded 1st edition (though it does seem like there is such a trend with shadowless and unlimited).
I’m wondering if anybody can shed light on this. Where I grew up, we never really had any 1st edition base set cards, so I never had personal experience with 1st edition base boosters or decks.