Oh, and a little addition - sculpting a dozen figures, preparing a mould and casting them costs money and lots of time and patience and requires some talent and skills. If you have some experience sculpting kneadadite you could sculpt a figure in one hour (assuming you're working with batches of a dozen or so). The mould takes about a day or two to make, three if making a two part mould. Casting depends on the amount of figures per mould and the time it takes to pour the resin. As the resin has a very short work time, you probably cannot pour more than one mould per time of maybe the aforementioned twelve figures. From previous experience I estimate about three casting cycles per hour per mould. You might be able to double this when setting up a production line. So after one week of sculpting and mould making you could start producing figures at a rate of 36 per hour. Material costs must not be forgotten - for a small amount of resin and silicone rubber you'll probably have to spend $50-$100, which fortunately will last for a while if you're not going to make any large castings.
Taking into account all these factors, you might realize why many people rather just buy Preiser figures.
Cost might be a little bit less when making very large quantities but you'll need much more Skill, Talent and Time.