I once bought a bootleg Final Fantasy VII Limited Edition OST (the massive one) on Y!JA in 2014 and somehow missed the fact that the discs had no (or very few) text on them. What's particularly interesting is that the fake discs were accompanied by everything else (the big black case, inner case, big booklet etc) and compared to the genuine item, it was more or less identical. There may have been subtle differences in the font (I think one sentence had bold applied, the other didn't) and colour quality (one had slightly brighter art) but I didn't have a third copy of the album on hand to compare. The seller was nice enough to refund in full and it was probably a genuine mistake (otherwise they wouldn't have taken a photo of the bootleg discs).
That's one of the few times I recall seeing bootleg game soundtracks on Y!JA. As opposed to eBay where it's like, 70% fake.
In regards to retro games, I see Japanese sellers on Y!JA selling reproduction copies of the more expensive/rarer games but at least they specify it is "overseas produced".