SEO and PPC have very different costs and results. For PPC/search advertising, your ROI is pretty clear. You spent X dollars, you got Y clicks, of which Z people converted. However, when it comes to SEO and content development, the results are much less clear.
When you put the time or money into writing quality content, you might not see any benefits in the first 30 or even 60 days. Over time, though, the more high quality articles you publish, the more your traffic will improve and the more it will benefit your search ranking.
This can make SEO very discouraging to pursue, but the results are far more sustainable. With PPC, you buy a click, and boom, it’s over. You either made a sale or you didn’t. With SEO, you are building authority and relevance, which will continue to drive traffic for months or even years. This makes it hard to convince someone just starting out that it’s worth the time and money, but when it comes to long term results, a strong SEO effort will pay dividends.