I don’t know about you, but sometimes I get completely overwhelmed with the sheer amount of time, energy and raw hours that go into properly marketing a website online. The thing that gets me the most is that with SEO and other forms of online marketing, there really is no situation when you can sit back and say “we’ve arrived.” Once you optimize a site, there are still so many things that can be assessed, analyzed, uncovered and corrected that you never really can say, “It’s Miller time!”
This is what I envy about web designers. They get to produce a finished work, then go and collect awards for their work. But, online marketing – that’s a different ballgame all together. Sure, we can celebrate top rankings, but tomorrow there is another keyword that needs improvement!
Good SEO Starts with Smart Purchasing Decisions | WebProNews

It’s probably not a good idea to purchase SEO until you are sure to have ROI. that's for sure.

I came to the conclusion that I will ever have a ROI (Return Of Investment) if I hire a SEO expert for my business, because profit margins are small and competition is extremely difficult to achieve against a saturated market.

What are your thoughts in your own market?