Wounded, Not trying to discourage but it's an awfully big project to start with but what the heck go for it.

I'm no math wiz and sometimes have to read things a few times for it to sink in. But.....the articles says
"It takes six and 1/2 batches (100 lbs. of cement) for each planter.". Not "100 pounds of hypertufa". That's a little over one 94 pound bag of cement per planter plus whatever the rest of her recipe (sand,perlite, vermiculite) included. It says that the planters weight 175 pounds and that was showing a planter with feet. Don't know if the feet are included with the "six and 1/2 batches".
To estimate your cost you need to know what recipe, what the cost is in your area for the all material including the mold and "L" bolts and the size of the finished planter, e.g. thickness of side walls and bottom and size of the feet. You're going to get real tired if you don't have a cement mixer.
Just an imagined recipe:
1 bag of portland cement (not concrete mix) 94 Lbs.
1 bag of builders sand 50 Lbs.
and the rest of the weight made up of perlite & vermiculite about 15 Lbs of perlite and 10 Lbs. of vermiculite. (just re-read this before posting and you can see my math skills 94+50+15+10 doesn't equal 175. I was thinking of a standard bag of cement)
What do those ingredients cost in your area plus the time and material to make that time consuming mold? Maybe I'm wrong but it would seem to be an awfully expensive mold.
It doesn't say if she uses any arcylic fortifers in her recipe which would add to her cost. Plus I forgot that she used a sprayer to apply her stain/paint so you'll have to add a sprayer and stain to the cost. WOW!
Maybe someone with better math skills has a formula. Good luck and keep us posted. Billie

I'm with Billie... this is really too large of a project for someone who has never used the materials before. All of Murphy's Laws apply to concrete and hypertufa, plus a few that are special to these materials.

You would be better off making some smaller planters, maybe a foot across and 6" deep, and get used to the materials, like how much water you should be adding (water in the recipes is always an estimate -- any moisture in the other materials will throw off the recipe).

Nearly everyone adds too much water in the beginning, when working with either concrete or hypertufa. Too much water makes a mix that slumps badly (collapses to the lowest point), and one that produces weak hypertufa. The kind of mix you want has absolutely NO RELATION to the concrete you see being 'poured' for patios, driveways and foundations.

Having a large batch of mix that is too wet tends to end up being a disaster, and you haven't the experience to know how to fix it in time (if it can be fixed) before it starts to set up. The usual remedy is a large hole in the ground, a considerable amount of frustration and cussing, and swearing to yourself that you WILL make several small projects to learn what is right and what is wrong.

What I have found amazing is that you can be mixing and gradually adding water, and you've almost got it just right, and then you add just another 1/4 cup of water and... it's too much. One stupid spoonful was all you really needed. Now you've got major slump and the mix just keeps creeping downward.

I'm sure you don't even need to ask me how I know this, right? Right! Been there, done that, and more than once, too.

Start small, and graduate.

Sue

First of all, thank you both for your replies. For some reason I never received notification that any replies were posted so I assumed none were. I began researching the subject and there was my post with your long and thoughtful replies. I did not mean to appear so ungrateful by not acknowleding.

One of my major goals with the tufa is to accommodate my container gardening cost effectively. Large containers are very costly in the store. But it appears that the materials for that large project are quite costly, so it does me no good.

I have bought a 95 bag of Portland, a 2 Cu Ft bag of Peat and 2 8qt bags of Miracle Grow Perlite (all I could find locally and quite pricey).

What I want to do no is use my laundry basket for a mold. I would form mine on the outside of the basket.

The basket measures 17" x 24" by 10".

Would anyone hazard a guess on how much of a batch I need? I have no clue if I need 5 cups of each ingredient or 50.

Spatially challenged...

I assume your basket is 24long.x17w.x10h.
I estimate a five gallon bucket each of Cement, Peat and Perlite would do the job if the walls are 1.75in. thick. It would weigh over 50lbs.
If it is 24long.x10w.x17h. a fourth bucket of total mix will be needed. It will weigh close to 70lbs.
This is still too large a project for your first one. Also, I assume your basket is plastic and otherwise smooth except for the holes. If the mix even starts to get into the holes in the plastic you may have to cut the basket out of the finished piece.
Start by making a few small pieces to get the hang of it and to develop a system for estimating how much mix is needed for other pieces.