I have all 3 sizes from Pampered Chef - spendy things, but the cheap scoopers I was using weren't holding up to the amount of use I was giving them. The small size makes a perfect 1 oz scoop (1 bath in a regular tub, but my friends with jacuzzi jets gets 2), the big size makes a 4 oz scoop (4+ baths). The medium size was abducted from the soap lab and is being held hostage in the kitchen for cookie making, so I never got to try it to see how big the scoops are and how many baths I get out of them.
Right now I am keeping the small scoops stocked and only using the big scoop for custom orders. The small scoops seem to sell better, most people pick out one of each scent, or if they're buying for kids they will let each kid pick out their own. I have them priced at $2 each, so they seem more appealing than bath bombs which I have seen starting at $5 each, going up to $15. I do pick my fragrances carefully so that I'm not going broke selling them at that price point.
Sorry, I know this was more than you asked... I'm rambly today