I'd pass on the one on the left, but I like the one on the right! (OK, for those who can't recognize "funny" when you see it, this was supposed to be a joke; I realize it's the same set. It's getting pathetic when I have to explain it to some! Sheesh!)
The 500 yen coin is worth $12.00. The other 3 coins are cheap because they have such high mintage numbers.
It is a custom set. Note that there was never an official Showa 64 mint set so this is a niche product. Some would pay a bit more for such set. Maybe $20 give and take? Could be quite wrong
1989 was Heiwa Gannen. It was the transitional year following the end of Showa. The set is not a Japan Mint issue. GXSeries is correct it is a custom set. Not worth anything special.