Did you check whether the seller had any recent successful transactions or feedback
Yeah, this is the first degree to get an actual point of view, esp. these days where scammers try hard to... ..well, scam people.
Not sure why this thread is separate from the official "bad traders" one, I suggest to publish in the dedicated thread : most people receive notifications on that one thread, making it easier to spread your feeling around.
[edited for small language corrections)
If you need help with a module I own/sell, I'll be happy to help, don't hesitate!