Why not do both ?
For example, Amazon do this all the time and are very successful at it. ie you buy one product but you have the option of bundling it with two or three other products at a reduced price
We do the same thing with tacamateurs.com and tacamateurs2.com. Two very similiar products but with totally different content. We sell them seperately but at the point of purchase, we offer them together as a bundle at a reduced price.
Heres an example
https://www.tacamateurs.com/cgi-bin/...TAC1&tacid=250
I'd say we get around 30% go for the bundle options shown on that page