I find that pricing SEO is complicated. Many firms offer one-for all packages. I think custom prices are the way to go, due to differences between business.

Anyone have ideas on how to price SEO?

I think you need a package deal, but also you need to have a rate per month based on the need of the customer. Do you do SEO?

I'm wondering that if you only do custom prices, many people might be a bit leery that you're doing some funky math on them or that prices are completely subjective and even arbitrary. They'll also feel the need to haggle and barter down with you.

I think any successful company needs some solid figures to work with. I understand that each industry is different - perhaps a solid pricing formula for a keyword ranking based on the number of results returned for that keyword ... or something like that. Just some sort of solid figure that people can hold onto. SEO is an industry where people shop around, and if they just get a vague price range from you, it's going to make them want to go elsewhere where they can see exactly what they're buying and how much it is.

IMO a monthly fee works best, they keep on paying as long as they get the results

You shouldnt necessarily price SEO on position but on traffic, which isnt always the same thing. A good SEO company will be able to find a niche for some of the keywords that your customers will be using and therefore gear your SEO towards that. This may mean your on page 2 even, but you still get the traffic.

since seo is an ongoing growing process, I would always do a monthly fee and base it on how competitive the keywords are.

I agree with Site Tutor, give a monthly rate and an indicative amount of work this will cover. That's what I'd be most comfortable with.