These services depend on what type of service you want. SEO has a technical, on-page, off-page aspect. It depends on what your needs are. It also depends on what keywords you want to focus on and how competitive it is. It is definitely worth it in my opinion, even if you provide top-class services or goods in your niche. If people don't know about it. It doesn't matter. Marketing is the most important thing and since most people are on a digital platform nowadays. Digital Marketing is the best option you have.
As #Sean78Black said, you must have to know what is SEO and how it will help you. Then just figure your what is your exact expectations from SEO services.
Definitely, you can hire the best SEO consultants but not sure about their prices. I feel their prices depend on your target and scope of work. Not all SEO agencies or SEO experts are expensive to hire. So you can find the best one on various platforms. you can ask them to show their previous work, and their strategy for your project, etc..
And just finalize the one who impresses you with their plans and work.