Sizes and the unit of sale
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The range
15 to 2,000 mL with a median of 225, and only 8 containers at a litre or more. The retail end is deep and the wholesale end is thin.
The hobby size
Small enough that trying a new colour or scent is a low-risk purchase. This is where a supply business acquires customers, and the margin per gram is highest here.
The working size
Enough for a production run without reordering mid-batch. A maker who has settled on a scent buys this repeatedly, and it is where the revenue is.
The wholesale size
Which this shelf serves least well. Eight containers at a litre or more is a short list, and a maker buying by the kilogram is usually buying in a bag or a pail from elsewhere.
Sell by weight, not by volume
Especially for powders, where bulk density varies between colours. A customer comparing two suppliers compares grams, and a volume-based range makes that comparison impossible.
Which means the container is chosen by what it holds
Not by its nominal capacity. A 100 mL jar holds very different weights of two different micas, and the range should be built on the weight the customer is buying.
Three sizes is usually the right number
A trial, a working size and a larger one. Each is a separate fill, label, lot and listing, so a fourth has to earn its place rather than appear by default.
And the smallest size is a marketing cost
A 15 mL trial jar costs nearly as much to fill, label and ship as a 100 mL one. Price it as customer acquisition rather than as a product and it does its job; price it per gram against the larger sizes and it loses money quietly.
Keep the sizes visually distinct
A customer with four jars on a bench needs to tell them apart at arm's length. Different container shapes across sizes do that for free, where the same shape in four heights does not.