I get half of the world traffic for the term "dirtbagging," on one page of my backpacking site, but that only means ten visitors a month. Without decent keyword demand you can't ever get much traffic. The amount of traffic you need depends on the nature of your site and products, of course, but nonetheless, a question: How much many monthly searches do you need to see before you'll optimize a page for a keyword? Steve http://www.TheMoneyMakerSite.com
My plan - although intermittently implemented - is to do as much on page SEO for it's targetted keyword phrase. Putting together an inbound link campaign is something I wouldn't do unless the keyword itself netted at least 150 visitors/day. My sites are all pretty low traffic, so a boost in 150/day would be something I would be happy with. I think it all depends on your target market though. 10 pages netting 15 visitors a day is also 150/day visitor boost and is relatively easy to accomplish if the keywords are low competition keywords.
I would add one caveat to nevetS statement. Some of my clients have high dollar retail items that are well worth lower traffic but, highly targeted searches. In those instances, I would still perform the link building due to focus and ROI. Hope that helps.
North Carolina SEO is right. It really depends on several factors. If you are running adsense, it depends on your CTR and CPM. I know of a site that caters to a very targeted market, sells nothing, but provides very detailed information that happens to have keywords that can pay several dollars. The Page CTR averages close to 100% - with some days exceeding 150%. That doesn't mean every person clicks an ad or two, but the content caters to such a specialized field where not a lot of "good" information is currently available, that it can result in multiple clicks per user because the site holds the readers attention. All traffic is organic, and the PR isn't very high. Being highly specialized, it isn't a high traffic site - and really doesn't have the potential to be one, however, in that type of situation, even 50 visitors a day can add up to a nice monthly amount.