I just bought a set (4) of NGK Laser Iridium Premium spark plugs ( IMR9A-9H) for my F4i. I called a few shops around here and was quoted anywhere from $19 to $25 a piece. Which is fine since plugs you don't really replace all too often, but then I found this ebay store. They weren't selling spark plugs but other bike and car parts so I thought I'd fire them off an email asking if they had them and for how much. They carry most bike plugs.
I got a full set for $47 Canadian including taxes and shipping.
I know they aren't a sponser on here and I'm not advertising for them, just giving you guys a heads up on cheap plugs.
I ordered them on Tuesday and they arrived today.
Here is there contact info.
Senior Sales Engineer
794 South Allen Street
San Bernardino, CA 92408