Burt's Bees Bubble Bath - Unlike some other bubble baths we enjoy, this version is tear free. I also love the scent on the kiddo - more milk and honey baby scented vs. herbal. The price point is decent $6-7 for 12oz, and you only need 2 capfuls per bath to make a whole tub of bubbles.
Method Squeaky Green - This one is my second-favorite scent, a sweet rice milk and mallow (as in marshmallow) light scent. It is consistently only $5.49 for 10oz. The bottle is a soft and adorable little seal. The main drawback to it, however, is the bottle design. Instead of unscrewing a cap, there is a silicone valve at the bottom, and you squeeze the thing directly over the tub. This masks how much you are using per bath, and I found that it took a big squeeze to get enough bubbles, so cost per bath is iffy. This bottle has to be stored far away from kids, and it leaks so you can't travel with it.
California Baby - Many parents won't let their daughters take bubble baths for fear of UTIs; this brand is so gentle that the girls can indulge in some foam! We enjoy it too, but at $14 for 13oz, a bottle of this is a real gift for the Nugget, something we tuck into Christmas stockings and Easter baskets. We gave out these mini bottles for party favors. The full-sized bottles come with a bubble wand, which is a nice touch, but actually problematic because you can't blow a satisfying bubble with the solution. It takes 2-3 capfuls for a tubful of foam. The scents are all essential oil-based; I really like the Cold and Flu version for winter.