So far on the forum I run I can honestly say I haven't spent anything on SEO as of yet. We are currently a page rank 2 all from backlinks from promotion techniques I use such as link in signature on forums I post on, link in profile on forums, top sites, forum directories and social networks.
I usually do SEO work manually myself. But I have spent loads of money on SEO In the past. I believe I have spent a good $500 on SEO for separate sites in the past. I do like doing it anymore. I have a person now that does it for me for free. Well he is more like a partner of mine which is why I get it for free.
Sometimes its good to do it but after a while your money goes to waste.
On my xbox forum i spend over £1000, but on my admin forum & my artwork blog, i have spent much. I will proberly spend more on them as time comes along, but for now, im trying to get my xbox forum getting thousands of search engine traffic
I have hardly spent any money on SEO, as I am capable of doing it myself. I do not see why people are spending thousands of dollars on a more than simple website, while they could actually buy a better template or software.