Me.
A hinted at in previous posts, there is a huge variance in price depending on the quantity / style / waste / finish.
For example, I can make 1 one-off as simple or as complicated as I like, dead cheap, but to duplicate it again will be expensive. The more complex ones will be in a square mould, which is easier to work, but incurrs about a 50% loss just in roughing round! I can cast in tubes, but these tend to be quite simple (solid colours, gentle swirls).
I tend to make sets of 3, which can be sawn into individual blanks, but again, these are difficult to replicate if they turn out to be popular. But they're a nice middle ground. I have several if they're good or if I trash one, but not so many that it's an expensive waste if they're not great. Also, swirling patterns in polyester is not easy. It's time-critical and that time is quite dynamic depending on a lot of environmental conditions. Consequently, certain blanks require me to sit over them for half an hour twiddling my thumbs waiting for the appropriate moment to swirl!
My biggest single blank was for a set of 12. These were for a customer. It was a sucess, but I only used the mould once: if I were to make a set of 12 and they turn out unpopular, that would be a total loss.
The result is that blanks can cost anything form $4 to $12.