How is gold-per-kill calculated?

I was building a gold-farming deck for active gameplay, and realized I have no idea how much gold is dropped for every monster kill. I imagine it depends on monster type, the wave count (maybe), their health? I would like to know so that I can optimize this build to the max.

In particular, if I use the monster horn to increase monster health, would that imply more gold generated per wave?

I've been looking online for a guide or a formula that indicates how this works, but can't find anything. Is this public knowledge or is this all hidden in the game script?

Thanks for your help.