Question about BSSB Parfait OP

[heroandflor.livejournal.com]

 Hello ladies~

How rare or how often does this dress show up on the sales comm?
And what would be a reasonable price for it?
In Google I found a couple of posts made last year, and a couple at the beginning of this year, but of course they're already sold. >.<'

Thanks so much~ and sorry if this is a stupid question.