What would they cost for sets of 4 or sets of 25 *without* the sale on? If you do this with the sale and discover that, yes, you can sell them for $3 - what does that tell you? Is that a price you're going to be able to continue to sell them at, and make a profit? If not, what price would you need to sell them at, when there wasn't a sale?

Because experimenting with expanding your product line, at a low cost, is nice - only if it's an actual, potentially sustainable, extension; otherwise it's just a use of time and energy and effort that doesn't net you much in the long term.

That being said, you have a bunch of stuff I think could be good cards, and I think they would sell well at Winterfest.