I just bought a set of 4 Jagwire "carbon" pads/shoes, NIB, for 4.99, shipping was $5.
I also got a ti set of Aztec/Delta's for $4.99.

Just an example of what you can find on eBay for $10.

Try searching on eBay for Kool Stop, Jagwire, Shimano brake, stuff like that.
I saw at least 10 sets of pads/shoes last night that won't hit $5.
There are lots of those 1-piece pads out there.

As far as flipping, simply tell them the pads aren't much good, and if the bike stops on the test ride, you've done your part. If you get into "I'll replace the pads,..." soon you'll be throwing in new bar tape, saddles, and skewers. If you're going to flip, inform the buyer well and don't worry about it.