I buy bulk in cardstock (it's a lot cheaper than buying individual sheets anyway) and only buy them individually when I need a specific color for a project but I don't need all the other colors (normally this happens with brown...and black, but black I get in a pack).

patterned paper I buy individually, although friends bought me a stack 2-3 years ago that I'm still going through (it's not what I would have picked for myself exactly).

The most recent set of patterned paper that I bought in a pack was this past year's Christmas Glitter Stack by DCWV. It was hugely on sale after the season and I loved almost every page in it.