You can tell which PC products will go up in price, though they don't make it easy.  They sent out the link for the Value Priced items in their e-mail promotions (and you can also find it via search - or could, they've been fiddling with their search engine). 

http://www.daz3d.com/value

If you check the Value category, any PC items you see there will go up in price after a couple of weeks.