Wants his money back? Wants his money back?! Ridiculous! He got what he paid for: a biological threat that would infest the neighboring country and drive people out. Something that would allow him to take over, but that couldn't be traced back to him.
Okay, so it spread faster than he expected, and crossed the border into some of his best (well, only) agricultural lands. So what? I warned him that it worked quickly. And then he sent troops in to deal with it? What was he thinking? He had the solution right there waiting: the fungus that would blight my man-eating plants. I gave it to him with his order.
Now he's complaining that he lost two companies of his best soldiers? So what? Do you have any idea how many minions I've lost over the course of two decades of cutting-edge research and experimentation? I don't have the figures handy, but it's a lot more than that. If I can make more, he can make more.
Honestly. Petty, would-be dictators these days. No, he's not getting his money back. I'll send him a nice crate of vampire porcubats instead.