You could just re-melt the sprue and use it to make the next batch, right?

What puzzles me is the lack of vent holes to allow displaced air out of the mold once it's assembled. (Unless they're on the other half, the one that's not pictured here. That seems doubtful.) So whatever this was meant to cast must have been a very runny metal with a low melting point, probably with the mold itself being piping hot as part of the process as well. Probably not much of an alloy, and probably very easy to melt again.

The inscriptions on these appear to be awfully similar to some of those listed here:

https://en.wikipedia.org/wiki/Xin_dynasty_coinage

Wikipedia mentions these specifically as being cast, and in big batches with multiple molds filled in one operation. In light of that I'm surprised that the mold is so small. Check out this sumbitch, for instance, which makes 42 coins in one go. That seems a little more like it, if you're going to go through all that effort.

I'm reading that apparently what with one thing and another, the Chinese were still producing cast rather than struck coinage all the way up to the very early 1900s. Their currencies changed a lot throughout their long and never-ending parade of civil wars, overthrows, usurpations, fractures, and reunifications, and it seemed every time their leadership changed it came along with a reinvention of all the coinage as well.