We are a small business and do most of our work in-house; however, I can share something that might help you to decide.
I agree with EGOL's take, particularly the part about risk. I looked at quite a few of the links you shared and they don't look so great quality wise. I opened them in tabs side by side and, though I am not an seo professional, it says link farms to me--cookie cutter websites, exact copies with different names, or similar looking with different names and colors.
We hired a very reputable company last year to help us rank for 10 key words, for which we received a very thorough marketing strategy report to enable us to do the work ourselves. The cost was in the neighborhood of $3,000. We implemented most of the suggestions and are satisfied that it was a useful expenditure.
They also offered to do linking and pr at various monthly prices. We didn't do that because it was out of our price range. For comparison, the price you are paying is in the mid-range of the proposal we received.
All of that said, I find that we've gotten more value from our Pro Membership here at seoMOZ and setting up a Campaign.