I have a client with a (relatively) successful niche market. In this market, there are CD's, DVD's and videos relevant to the accessories the client is selling.
However, she cannot stock these items because they move very slowly and to buy a wholesale quantity that would create any kind of profit margin she'd have to buy more than could be moved in a reasonable amount of time. So say, example, she's have to buy 100 and would maybe move 2 or 3 a year. Not good. :-)
Second, many of these CD/DVD providers simply don't do wholesale. They give you 10% off. Period.
These are available retail everywhere else anyway (Amazon, eBay, etc.) But people come to her site looking for them, to the point of contacting and asking. You would think, well then, she should sell them - but it's just not cost effective, see above.
So we were toying with the idea of listing them on the site as affiliate links to the other "outlets." The affiliate widgets would appear along side other related products, but would be clearly marked as off-site items, "buy it from XYZ."
The first thought, of course, is once they leave the site they may not be back to buy the accessories, but it's been her experience that people come looking for a specific thing, and rarely delve into other areas - for example, if I buy a shirt, I'm not looking for hats or pants (anonymous reference.) Someone looking for DVD's or videos is not likely to be shopping for other things.
Or is this a deadly dangerous idea? I've already said, straight up, "I don't know." :-)