Doing SEO for your website is not always very expensive and difficult to do, especially if you have a very specific niche and a website with solid age. Nowadays SEO strategy and tactics became very obvious, you have to make your website for your visitors if you want long term permanent results.
Almost everything you do on your website and off your website for your visitors convenience etc. reflects on SEO. Even new Google's algorithm says the same thing, more attention is shown to good content, social sites, links from related sites etc.
So doing real organic SEO can be affordable and the results will be long term, of course it takes time, but the longer you worked on specific keyword, the better results you achieved.