SEO freelancers are typically cheaper than SEO companies. Like companies, freelancers have different rates, which depend both on the freelancer and your business. For example, your business profile, niche and goals can alter the rates, but at the same time, experienced workers will obviously charge you more.
The main difference between freelancers and companies is the volume. A company will have more consultants, each of them specializing in a certain thing.
Plus, some companies assign a dedicated SEO manager to each project. A freelancer, on the other hand, handles more projects at once. Therefore, results could be a bit slower.