You have to look at it this way.
With your product Look at what your profit is on the product.
You should figure in product cost, shipping, staff, advertising, office and so on.
once you figure all that in then you will have what it cost you per product. Look and see what you really make at that point.
Now you would have your profit per item. Of that look at what you would be wiling to do out of that as a commission.
Really its up to you and what works best for you. yes not everyone is going to promote your product because they want more money.
The people for a product would be getting users to sign up because if they like the product they are going to tell friends.
A true affiliate marketing rep really cares less about the product they are just looking at how they can make money