Quality links are far more conducive to solid rankings than plugins.
You have to prove that by showing us the ranking metrics of some of the sites you mentioned in your post, you have to convince your client not on the number of articles that you can provide but the return on investment that they are going to get from your package, so let's say from this package
$1,850 for a website with 1,000 articles.
What's the projected return on investment, and what kind of monetization is applicable?
We are happy to provide SEO consulting free of charge as a courtesy to ensure customers don't waste money on useless or even detrimental links like the ones found on let's say Fiverr.
I have seen Fiverr freelancers with hundreds of testimonials and getting excellent to good ratings what do you have that you think you are better than these freelancers?
We provide free SEO consulting and do not offer link building services because we want to avoid conflict of interest situations that arise precisely because so many people want results as soon as possible.
Yet if you play it safe, it can take well over a year until steady search engine traffic emerges.
The conflict of interest would arise because it would be in our best interest to get those sites ranking right away by for example deploying blackhat link building... the customers would be impressed and proceed to order more. Yet BH link building quasi-inevitably leads to penalties that jeopardize or even compromise the entire project. What good does it do if you get 15 minutes of SEO fame if a penalty quickly follows?
The same principle is valid for most Fiverr links. There are many, many providers with hundreds of positive reviews who sell hundreds of links for a few dollars. I personally think buying those links is a bad idea if you are in it for the long haul, if you believe otherwise then that is your prerogative.
We do not promise fast results and just like with any venture, there can never be guarantees. What we do promise is that we will do everything humanly possible to build you a site you can be proud of. While not as exciting as a get-rich-quick proposition, it's at least an honest starting point or a solid foundation, if you will.