Pay Per Click - what is it?
Every industry has certain keyword phrases you cannot rank for, no matter how hard you try. This is when PPC is a perfect idea. While as high as 80% of people do not look at the paid ads (they only look at organic results), if you can’t rank organically, then the only way you can get on the first page is by buying ads.
Short term solution
PPC should not be a long term solution but rather a short term solution to getting found for difficult keywords. Why is that? PPC is costing you money every time someone clicks on your ad and there’s no guarantee it will result in a sale. Every dollar you spend on ads is gone and the only thing you have to show for it (hopefully) was a few sales.
When you spend money on SEO, you are making an investment in your website as the improvements (to your website) don't go away. For example, the pages of content you add will be there (theoretically) forever so as you keep adding content, it builds upon itself to make the entire website stronger and perform better. This results in a website that increases in strength and power as time goes by.
How does this work with PPC?
If you invest in SEO, you may be able to start ranking organically for some of those keywords you had to buy ads for in the past. You can then shift the paid ads to other keyword phrases or if you didn't have much success with your PPC campaign, you may want to invest that money into an expanded inbound marketing campaign. After all, if the money you're investing in SEO/inbound marketing is working; imagine the results if you invest even more money.