Spend-based points with package awareness
A spa visit can range from a $50 facial to a $400 day package. The loyalty mechanic must accommodate that variance. Spend-based points, with bonuses for package purchases, is the right default.
A 1.5x points multiplier on package purchases rewards package adoption without distorting the per-visit math. Packages are the highest-margin product most spas sell; the loyalty program should push customers toward them.