I was just wondering, what is the most expensive blood that gets restocked, and if everything more expensive than that doesn't?

Basically, how do they determine which ones get restocked?

Expensive blood is hardly restocked. I have decided everytime I must restock from medium-higher end stock, they will also go up a bit in price because they're obviously in high demand

The lower end items will be restocked whenever we see fit. Otherwise, go to the Tradecenter or Marketplace.