I looked at that used battery grip for weeks on B&H since I saw the prices increasing on them. Decided against it since I'm not sure when/where/what the K-3 II successor will use or be released.
I think they raised the price partly to make themselves look more valuable. They'll claim Yen change but I don't think that is the whole story. Especially after their recent interview where they said they wanted to be "premium". Plus, they are including it with K-3 II sales and touting a 299 dollar list price, which makes the bundle look even better.
The rest of us know the item hasn't sold at 299 until now.
It was half that price for most of this year.