Backlink wholesalers to DIY

Fatjoe, Authority Builders to name a few. What’s your experience with these and do you have any advice? Would rather DIY it than pay agencies a massive markup and monthly retainer who are basically gatekeepers to high DA sites through relationships which these wholesalers have access to and sell much, much cheaper. Problem is you have to know what you need strategically and based on your category and wha your competitors have. What advice do you have and are any of them better than most? What’s your experience with them?