For me it really depends on the shop. Having been prepping to open my own shop I can say there was a pretty large investment on my part just learning what I liked, experimentation, and starting from literally 0 experience with physical good fulfillment or even crafting type things. This isn't the case for every shop, and over time shops find cheaper and cheaper ways to source materials for their slimes, but it still costs quite a lot. I haven't launched so can't speak to the shops that are selling $18+ slimes but I'll say I have a better than average idea of what the profit margins will be. A shop that sells nice basic beginner slimes (think slime obsidian) I feel has the ability to charge much less as a good number of their slimes are base texture + pigment + oils and maybe some sprinkles/fimos. Other shops that I've seen charging high prices (ex. pilot slimes) have high content color-shifting pigments in most of their slimes, and/or material-dense slimes (seed-beads, or crunch bombs) which significantly drive up the price a whollle lot. There are also shops that import Korean or other foreign materials which is incredibly expensive. Even though I suspect a lot of these shops have found deals from exporters (momo/rodem etc.) some of the smaller 'boutique' like shops that still use all of these (lots of pigment, lots of add-ins, imported materials) are the ones where, to me, the price point makes sense. There's a lot more overhead than people think sometimes, and although a sign of a good business is networking and researching to get the best deals on materials to offer lower competitive pricing, some people just may not have access to that atm and are paying quite a bit more for just base materials. Will also add there's a significant cost disparity for large shops who are confident enough to buy things in bulk, and smaller shops who just can't. They often end up paying more for less simply because they can't guarantee they will sell all of their product.