A day pass or drop-in rate serves a genuinely different purpose than a membership — often a traveler, a trial visitor, or someone testing the gym before committing — and pricing it purely as a fraction of membership cost misses that distinction.
Price it to encourage conversion, not just to charge for access
A day pass priced to make membership feel like the obviously better deal for anyone visiting more than once or twice supports conversion, rather than pricing it so cheaply that there's no incentive to commit.
Track who converts from drop-in to full membership
Watching how many drop-in visitors eventually convert reveals whether the day-pass price and experience are actually functioning as an effective trial, or just as one-off revenue with no follow-through.