Bonuses are items offered as free extras if someone purchases your main product. In many cases the customer can keep the bonus items even if he/she returns the main product, but that’s not a rule unless you advertise it that way to prospective customers.
One obvious value of bonus items is that they increase the perceived value of your offer. The prospective customer sees themselves as getting more value for their dollar if they buy your main product. Offering to let the prospective customer keep the bonuses even if they return the main product really makes them feel like they are in a good position. They feel they can shell out some money (only temporarily) just to get the free bonuses and then return the product.
Yes. A certain percentage of your prospective customers will do this. What you have to believe is that not all of the people that do this will actually return the product. They will either see it and like it, or never get around to repacking it to ship it back. Thus, there is a net gain for you.
The important thing to remember is that more people will pull that wallet out to buy than would have had you not offered this incredibly good deal. When you are offering downloadable products as the bonus, then when someone returns the main product, you won't even incur any costs other than a little administrative time.
A rule of thumb is that the bonus you include should be so valuable that you could sell it if you wanted to. In fact, many marketers use bonuses that have been sold before. Multiple bonuses will generally get you more sales. Of course, if you use downloadable products you won’t incur any more costs to include them.
Selling on the Internet is easier than you think...