The difference is mostly to do with user experience. It also has to do with the requirements of how you bill the customer. It means you can't give them a "free" sign up and then charge them a fee after the click the data selling opt out button.
What's meant by saying you can offer incentives is that you must present all information at the same time and that users are considered as opt-out by default.
Basically, the user must go through a sign up page that has a box that says "You may sell my data in exchange for a $3 discount" and it cannot be selected by default. You also cannot have a sign up page that has a box that must be selected to opt-out whether the box is selected by default or not.
The no-relatiation clause also has addition requirements that are not related to money. For example, you cannot refuse to allow a user to access your site because they didn't allow their data to be sold. You also couldn't impose access limitations like slowing the rate of page response or increasing the number of advertisements on the page or send spam only to users that opt-out.
The difference isn't really about charging a fee to users that won't let you sell their data. It's more about not allowing websites to harass users with increased advertising on behalf of whoever they wanted to sell your data to. It's only illegal for them to sell the data, internal use is still legal, so they're preventing a loopholes.
What's meant by saying you can offer incentives is that you must present all information at the same time and that users are considered as opt-out by default.
Basically, the user must go through a sign up page that has a box that says "You may sell my data in exchange for a $3 discount" and it cannot be selected by default. You also cannot have a sign up page that has a box that must be selected to opt-out whether the box is selected by default or not.
The no-relatiation clause also has addition requirements that are not related to money. For example, you cannot refuse to allow a user to access your site because they didn't allow their data to be sold. You also couldn't impose access limitations like slowing the rate of page response or increasing the number of advertisements on the page or send spam only to users that opt-out.
The difference isn't really about charging a fee to users that won't let you sell their data. It's more about not allowing websites to harass users with increased advertising on behalf of whoever they wanted to sell your data to. It's only illegal for them to sell the data, internal use is still legal, so they're preventing a loopholes.