have had about 1,000+ or so large prismatic shards or so that where hard to sell. I needed quick cash but these shards would just not sell.. so what I did was this. I spammed trade "Want to Sell Large Prismatic Shards, CHEAP! Resell for quick profit". I have gotten a few whispers, but they where not convinced they could make profit buy buying these off me. So I gave them one large prismatic shard for free and told him to post it on the AH for higher than my selling price (IE, I was selling them for 5g ea, I told him to post it for 8g+ on the AH) and then I bought it on one of my alts, making it seem they where easy to sell.
Then sold him over 10 stacks of large prismatic shards ^_^. Worked great in the end, esp with a item your selling in bulk.
You may want to say something like "If you buy a stack for 5g ea and then resell them for 8g+ you will easily make 60g profit!" to convince them further into buying it.
Just wanted to share, havent contributed in a while.