Affiliate bonus offers increase your commissions in a variety of ways:

1) By increasing the value of the purchase without increasing the cost, they increase total sales.

2) By increasing the value of buying through YOUR affiliate link, they funnel the commissions from more of those sakes into your account.

3) The value of buying through your link also reduces the probability of them substituting thir own affiliate link.

Here’s a video showing one of my first affiliate bonus offers.