The Halloween event (?) where you farmed coins from dead things caused an influx of both dead branches and bloody branches into the market, I believe. A low cost prize to exchange these coins was a certain amount of both the types of branches.
Probably seen as the most enterprising decision, and therefore, was farmed over the period of the (fairly long) event. Everyone has them, they have to compete to sell them, which ultimately drives the prices down. It will stabilise eventually, as it is a one-time-use item, but it may take a considerable degree of time.
