I think selling information products isn’t profitable for every blogger. I know blog owners who are earning pretty well, around 5 figures a month, than they could from affiliate marketing or selling info products. Some of them even tried to sell third-party products, mostly Amazon, but profit wasn’t near what they were earning from AdSense and other forms of advertising.
That being said, it really depends on the type of audience that visits your content. For example, people who just visit your blog to read news tend to buy far less than those looking for the solution of a problem. Just image a Facebook user who saw a viral post title and clicks to read the whole story. He is unlikely to purchase anything from your blog unless he finds something really compelling that matches his interests.
That is why most news and other viral blogs only use AdSense on their websites.
On the other hand, if you’re running a blog that provides solution to a particular, selling physical and digital products makes more sense than displaying CPM ads.
In Sarfraz bhai’s case, he targets PC audience which is interested in learning how to build a PC, so people buy related physical products. If he creates an information product around the same topic, that will obviously be profitable as he is already receiving audience that is looking for solution to a particular problem.
I hope this helps!