I went through two sets of "good" second hand OEM coils before getting Yellow Jackets.
If my car was my daily, and I had the choice of running YJ for $400 or OEM for $800+, I'd go YJ because 1. my car is standard, 2. I can get the YJ in a couple of days, whereas who knows when the OEM ones would come. If I was running 20psi on a build motor, I wouldn't even consider anything less than OEM. Like I said, my set has been flawless for 2 years daily driving + two track days, yet people have had bad experiences with them almost instantly. It is what it is, a cheap alternative. People had good results with them as well, obviously not on high output motors.
I'm not saying YJ are better than X (I'm not affiliated with them, not endorsing them), what I'm trying to do is give audience of this thread (a public forum) a view from a non-built-motor perspective. People with faulty YJ coils had good replacement experiences as well.
This post is for the poor/tight arses who are looking to spend minimal but have something that'll (hopefully) last a bit longer than something even cheaper. But these days OEM is a lot cheaper, so if I were to buy a set now, I'd get OEM.
If that is legit original, then great buy! I'm guessing seller got it from UAE? Wonder why they're $50 from there, but $100+ from Japan.