Growing an arts based business is often quite different than other product based businesses. Social media has been a powerful sales channel for artists, but it takes some skill. You’ll want to link a Shopify store to your IG. You’ll also want to invest in either paid ads or paying to boost posts to get stronger traction. I would also look for other arts based online selling platforms. The more places you can be, the more exposure you’ll get. I’ve also seen artists go on travelling road shows, booking space in hotels to do small showings.
I can appreciate how difficult it is to get a handle on your costs as an artist. It’s tricky to value your time appropriately and know how much of your materials are used in any given piece. And there’s also the difficulty of accessing materials in big enough volumes to access preferred pricing. I would recommend talking to other artists to learn their tips and tricks. It’s possible, if you get to know other soapstone carvers, that you might be able to bulk buy materials together, to get the volume required to access the better pricing.
I hope that helps!