I've purchased a lot on kijiji and unless I see something terribly wrong with the item, I pay the asking price. I recently purchased an adult 10 speed bike from someone locally...when I expressed an interest but couldn't make it out to see it right away, they said they'd hold it for a few days for me. When I saw it, it was a fair asking price, so I added $10 for their courtesy in holding it for me.
I have sold a few items as well...and inflated the price on purpose so that I could negotiate down to the minimum I'd accept.