Welcome to the forum CroMagMan! Do you both have your own accounts, or are you going to share one account?
Depending on your choice of ingredients and your choice of equipment, the cost of making soap can vary quite a lot! I can't even start to tell you what the cost per bar was when I started out. I was just learning to make soap and that's all I really wanted to do at the time. Also the size of your bars will impact the cost per bar and how much waste once you cut and trim or bevel or otherwise clean up those bars. (But I do give a cost per bar example in the 2nd to last paragraph.)
When I was new I used recycled material for soap molds, so that did not have to figure into the cost of making soap. I just cleaned out milk cartons, margarine tubs, ice cream tubs and the like to use as molds. Although once I started buying freezer paper to line molds, that would have factored in, but a box of freezer paper actually lasts a long time. Later I started buying molds and cutters and other adjuncts to use as design tools. That gets quite expensive when you let it.
And the oils I used were usually the best price I could find at my local stores. Prices vary from store to store and it's easy enough for me to do a price comparison in my little town with not very many stores to visit. I did not start ordering oils online until I'd been soaping for several months, so I was limited to what oils I could find near me, and those were pretty limited. The oils I used at first were: Olive Oil (grocer - average cost at the time), Coconut Oil (on sale at good price), Castor Oil (expensive in pharmacy section of Walmart), Cocoa-Butter (expensive at Dollar General in lipstick-type tubes), Almond Oil (used to be sold in grocery store, but no longer available there), Grapeseed Oil (grocer), Vegetable Shortening (grocer - sometimes cheap), various other oils as I found them in stores. I tried many different oils just to see what they were like, but mostly it was just for fun and experimenting, which is good in my book.
Other factors when considering expense of soap: Distilled Water (grocer or WalMart - cheap); Lye - NaOH (Tractor Supply Company - expensive), fragrances (expenses rise exponentially when you let it), colorants (expense can go sky high if you let it, but you can start out without any colorants and that's fine, then experiment with naturals like carrots, tomato juice, spices, then look into soap safe colorants from soap suppliers).
When I say expensive above, I am referring to the 'per ounce' cost as it compares to buying from a soap supplier. For example, I can pay approximately $15.00 for a 32 ounce bottle of lye at TSC (Tractor Supply) or get it at a far better per ounce price from a soap supplier online. I save a lot of money doing that, but in the beginning, I bought locally and was fine with that at the time. Others find lye at ACE hardware for a fairly reasonable price; I did once myself while traveling, but not anywhere close to where I live.
So I know that doesn't answer your question. But it should make it evident why it's a hard question to answer with any specificity. But I'll try and give you a cost per bar if I were to make uncolored and unscented Castile soap at today's prices for oil, lye (at TSC) & distilled water today: Lye=51¢ per ounce; Distilled water=under 1¢ per ounce; Olive Oil=26¢ per ounce. Using a
lye calculator such as
this one, you can get the answers yourself as you can enter all your supplies and their costs into the database before you even make the soap. But here's what I come up with for a batch with 32 ounces of olive oil: $10.27 to make this batch. The total batch size is 45.31 ounces, but 18% of that is water weight, which after cure should all evaporate, so I would end up with 37 ounces of soap. If I cut my bars to way I LIKE THEM (we don't all cut our soap bars the same size or shape, so this is purely subjective), then I'll end up with say 8 bars of soap. Considering some loss from planing & beveling, then I'd end up with 8 bars at maybe 4.5 ounces of soap each. Each bar of soap would have cost me about $1.28 to make. But that doesn't account for my time, my electricity or even my gasoline to go shopping. Once I start adding more ingredients and different oils into the soap, the costs per bar are going to go up quite a lot.
I doubt my soap is as inexpensive to make now as a plain-jane bar of Castile soap. I'd be willing to bet that they tend to cost me at least double that or more these days, when I factor in the other materials I use. And that's still not taking into account electricity and my time.
