http://official-gomk.anonblogd4pcarck2ff6qlseyawjljaatp6wjq6rqpet2wfuoom42kyd.onion/p/if-you-re-not-paying-for-the-product-you-are-the-product
This assumes that the people who offer free stuff are selling your data in some way. Many websites have a Privacy Policy where they outline what data is being collected and how it is being used. If a website points out that there are external links and that it is the user's responsibility to be aware of how those websites collect your data and to enter at your own risk, then in a way, yes, you're still the product even if the main website isn't actually selling your data...