Actually I've been in this business for 5 years and worked in both agencies and content companies, so I have more insider knowledge rather than experience as a customer, hope it's ok.
Most agencies are just hiring freelancers and putting a 10x markup on it. Since they're probably using multiple freelancers per customer, they can't guarantee consistency, which is why they need internal reviewers (which adds to their overhead).
The strategy part is not a lot of work, and I've seen the people that do it working with up to 50 customers simultaneously, so it's not as if it takes a lot of time. 75% of the secret sauce is just picking words out of SemRush. I'm not even joking.
The best ROI right now, IMO:
1. Have one or two good freelancers you trust. You'll have more consistency in your texts and you won't have to manage much. Most freelancers already know how to do the SEO part, because agencies already hire them to do it. They're cheap, so it is easy to "test" them before committing. Good freelancers are low-maintenance.
2. Outsource the strategy to a freelancer. This way you won't be tied to an expensive contract with heavy fines and they'll be able to spend more time. Sometimes they'll also produce content, other times they'll be able to manage other freelancers for you.
3. In my experience, most agencies use run regular consumer tools behind the scenes: Buffer, Semrush, Moz, Mailchimp, Hubspot, and A LOT of Google Docs. SEO checking is done using Yoast, which is free. Most of those tools are simple to use.
Most agencies are just hiring freelancers and putting a 10x markup on it. Since they're probably using multiple freelancers per customer, they can't guarantee consistency, which is why they need internal reviewers (which adds to their overhead).
The strategy part is not a lot of work, and I've seen the people that do it working with up to 50 customers simultaneously, so it's not as if it takes a lot of time. 75% of the secret sauce is just picking words out of SemRush. I'm not even joking.
The best ROI right now, IMO:
1. Have one or two good freelancers you trust. You'll have more consistency in your texts and you won't have to manage much. Most freelancers already know how to do the SEO part, because agencies already hire them to do it. They're cheap, so it is easy to "test" them before committing. Good freelancers are low-maintenance.
2. Outsource the strategy to a freelancer. This way you won't be tied to an expensive contract with heavy fines and they'll be able to spend more time. Sometimes they'll also produce content, other times they'll be able to manage other freelancers for you.
3. In my experience, most agencies use run regular consumer tools behind the scenes: Buffer, Semrush, Moz, Mailchimp, Hubspot, and A LOT of Google Docs. SEO checking is done using Yoast, which is free. Most of those tools are simple to use.