In short, yes. But this is obviously not Google's concept behind "buying" links. If you read my comment above I explain about what Google cannot possibly class as a "purchased" link. Here is a snippet...
"For example, how can Google tell if you are buying links? It could be that you have a next door neighbour with a very genuine website and you get a link from his site in return for a pint of beer at your local pub - Google have no way of knowing this! However, if you aren't very careful with your footsteps and you openly sign up to places like BMR which clearly advertises paid links then at some point you will more than likely be found out."
You would be wise to understand that more often than not, the value of purchased links is nearly always less than the value of a manually built link based on good, unique and relevant content on a page which is from a trusted domain and has very few links on the page.
As always, the key here is accountability and covering your tracks. I'm not telling you not to buy links. Im saying you would be wise to put all your eggs in the "purchased links" basket. If you must purchase links then ensure they are of good quality and cant be traced... more importantly, make sure they only cover a smallpercentage of your overall link strategy.
Lastly, I just want to comment on your comment:
"Every site in a competitive market buys links"
Not true. I agree that most do, sure. I also think that most do not understand the dangers and pitfalls of buying links. They probably also think that the more links the better,., regardless of quality of link and the quality of the content on their site.
I used to own a multimillion pound-a-year eCommerce company until I sold it last year and I can honestly say that I had never once purchased a link for the site. We were position #1 in Google for over 300 keywords and the largest eCommerce company in Europe for our specific Niche. Just so you understand the competition, our main keyword which we ranked #1 for brings back the following when searched:
About 740,000,000 results (0.18 seconds)