Brian 18$ a pound x300#s is $5400 a week-or 21K per month-thats a lot of selling. Not sure why you need this much from clay?
I have a few thoughts
My suggestion is keep your expenses down.
I buy in bulk-everything
I always have as soon as I could afford to
I never thought I would not be in clay so it was easy to think more is better
I bought in groups with other potters
Now I do the group buying for many potters its come full circle
Since I never have tried to support myself with electric kiln firing (always more gas than electrics) so I have little data on that end-
I can say that a diversified selling base is best.
I started out my now over 40 year career very slowly and with very little.I scratched it together slowly never crunching numbers or thinking I had a plan or for that matter considered it work. I loved clay and making pots-got to sell a few along the way. It never paid well but got me by. That was for many years until I made some break through's
First I never considered this life it just happened and even today I'm amazed people pay me to make pots in my studio.I was in the 70's and its still true
I will add I have zero idea on an hourly wage-never have-I know that's shocking for some
Now its a major business and its been a great job and life.
The question is how each of us gets to that spot
One of my thoughts is do not over think this or expect to much to soon.Making pottery for a living takes time takes lots of work and connections and customers-this all takes large amounts of time.
I have a friend who is 30 and is on this very path-Its his second year doing shows on his own.I took him to a show as a paid helper last spring just once so he could take from me some things he could use in his business-Learning from old timers is one way to add to your business. I really want him to succeed as at least where I live there are no young potters taking over where us old timers are leaving off. He did work for a full time potter during high school so he saw what can be done.
I suggest you try to diversify sales-some wholesale some shows some whatever-that way you cover all the bases and as you grow this will pay off or at least it has for me.
I do not have a scale as you posted as my scale is what profit is left over each year. In Ceramics we can really add to the expense column-the trick is to keep it low as you can.
I bought a lifetime of some materials 40 years ago so figuring some costs are just impossible but this has kept me from trying to do that math do much.
(Mea is rolling her eyes now)
I'm willing to talk story about any of this with you in the next two days or when I return from my big show-as this is my crunch month.
Just pm me your phone number and when is good time to call- I'm just about packed a few days before leaving (this is another key point about being prepared) I'll be back on the 9th
Other than talking direct (which is best)
I will have to think some more on tips for your business.
Keep positive if clay is for you you will stick thru the down times as there will be some.