It seems that Kumos Day Figurine is worth like 10 mln, but it's worth only 90 k

I believe this is because some people use smaller priced items to pay for things like art. This kinda throws off the balance when that happens.

40x: Black Broken Bottle @ 1,072,276 sP = 42,891,040 sP ^ It happens to me too xD

I don't really think there is a way around that.