Design stage:
Is free! :D You can design your doll on a piece of paper, this process will only cost you whatever time you put into it. I drew a 2d image of the doll in SketchBook app on my tablet and the 3d model in Sculptris on my computer. Having a drawing really helps with 3d modeling later, especially if you have never sculpted in a 3d modeling program before, as you can put the drawing and model side by side to check sized and proportions. My 3d model ended up looking different from the drawing, but the sizing and overall appearance was close.
The hardest part was using Blender to cut the model and create joints. Sculptris is amazing and easy program to learn, but unfortunately it lacks any features needed to make separate doll parts, so you will have to use some other program to cut up whatever you design.
Overall cost: Software - free (any digital drawing application, Sculptris, Blender) + cost of your time learning the software and using it to model.
Prototype manufacturing:
I used a PrintrBot Simple with heated bed to print all parts of my doll at home. I printed the torso and head parts in halves and glued them together, this way I did not have to deal with the support material and the printer produced nicer surfaces, but I did have to even out the seams. Everything else was printed in one piece and some support material had to be removed. The main disadvantage of printing things at home was that even with 0.2 mm nozzle our printer does not really print in resolution high enough to produce smooth surface. The parts had almost spongy texture and this obviously created more work, sanding took a long time. The main advantage of printing at home is that I could try different scale to see how big I wanted the doll to be and did not have to wait days for parts to be shipped to me from a printing service.
The sanding was much harder than anticipated. I have never sanded many tiny plastic pieces to smooth finish and did not really know how to do it right. I used 2 cans of Rustoleum Automotive Primer Filler, 2 cans of Tamiya fine Surface Primer on top and sandpaper grades ranging from 400 to 1000. I actually tried many different types of sand paper, I think 3M softback sponge and Mr. Grinding Cloth were my favorite. And I have only found out that 3M sponges come in much finer grit when I was mostly done with sanding.
Overall cost: PrintrBot Simple costs about $700. You can buy a smaller Play model and attach the heated bed, which should cost about $500. Spool of PLA filament - about $20. Rustoleum $5x2 = $10, Tamiya primer $12x2 = $24. Mr. Grinding Cloth $6x2 = $12 (2 sets of rough and regular mesh), 3M flexible sanding sheets $5, 3M softback sanding sponge $5.
PPE: respirator with OV cartridges $30, dust masks $7, glasses $7, latex gloves $8.
So assuming that you do not have access to a printer, the total cost with PrintrBot Play would be $628. If printer and filament are accessible to you, sanding and PPE would cost $108. I may also add a cost approximation of printing through Shapeways if I find time to do a quote. Add cost of your time to set up and supervise prints (if not printed through a service), cleaning up support material and hours of sanding loose doll parts.
Casting:
Gets really expensive! :D I cast my doll essentially to see if it was possible to do without a compressor and a pressure pot. The answer is yes, but not for distribution. After fiddling with my molds I eventually managed to produce a singe doll that did not have giant bubbles in the most noticeable places. She does have lots of embedded bubbles and cavities and I would not be able to sell dolls in this quality. I however do enjoy styling, dressing and photographing her, so she does live a full life of a loved ball-jointed doll regardless of all her flaws.
Overall cost:California Air Tools 5 gallon pressure pot costs $214 on Amazon. A pancake compressor would cost about $120.
I used 4 kits of Smooth-On OOMOO 30 silicone $25x4 = $100. Release agent $17. Craftsmart modeling clay $3x2 = $6. Silicone is cheaper to buy by gallon, but it also will eventually expire once opened, so I decided to buy smaller pint kits instead as I was not going to make all the molds at the same time.
Alumilite Amazing White resin kits $24x2 = $48, dye $5x3 = $15. I did buy 3 different dyes thinking that I will be casting rainbows and unicorns, but it will take me a while to go through all this dye now that I know how much work it takes to cast anything.
So if you are like me and just want to stubbornly try to cast your prototype without a pressure pot, it will cost about $186. Doing it right would cost about $520. Add time for assembling individual two-part molds for every doll part, pouring and curing silicone (OOMOO 30 takes 6 hours) and pouring resin.
Miscellaneous tools and items: you may find some unexpected applications for everyday items. I used a lot of shot size paper cups for mixing silicone and resin, popsicle sticks, toothpicks, coffee stirrers, straws, free measuring syringes from pharmacy, cardboard, lots of newspaper and paper towels. Many people also use lego bricks for building mold walls. Luckily you can buy these by weight on ebay!
In the end if you have access to 3d printer and do not plan to distribute your doll, you can make one for about $294. If you have to buy a printer and want to be able to produce quality casts, it will cost about $1148. This cost estimation is for a 17 cm single-jointed doll. The cost will go up depending on the size and complexity of the doll.
Conclusion?
After looking at all the materials and the amount of work it takes to make a BJD, it seems the real expense is the time needed to learn how to use the software, tools and all the materials. I have a regular day time job, so my doll took me a year and a half to make. Even though doll making can get expensive, occupies obscene amounts of time and can be pretty frustrating when things do not go right, it is a very satisfying experience for an obsessive maker.
