A few words from the other side of the fence:
I commission a lot of art, and have heard a lot of horror stories from artists about clients, ranging from passive-aggressive footdragging to insane non-sequiturs ("I'm giving you exposure ! You should pay ME !). (Apparently there's even a site out there collecting the most absurd client stories)
I was so determined not to be that type of asshole that I went in completely the opposite direction. I always pay in advance if they ask me to. I answer mails practically the second I receive them, and I'm always respectful, patient, appreciative and enthusiastic (it helps that I only commission people who's skills I genuinely admire), and I don't bother them while they work.
This works pretty well, except when it doesn't. Currently I've been scammed to the tune of about 500$ in total, and being ghosted for over a year is nothing new. Frankly, I prefer that to some of the responses I do get, which border on comical : "Hey man, I'm depressed ! Leave me alone !" or "if you can afford 100$ for a drawing, then you're rich enough, so why should I give it back ?".
Thing is, some people are assholes, and internet communication doesn't encourage empathy (or even basic, everyday honesty).
You handle it by shrugging it of and moving on.