I have never bought backlinks for my blogs, simply because I'm too cheap to pay for them. But I have sold a heck of a lot of backlinks over the years, I was selling backlinks on a PR5 blog of mine for $100 a year which were very popular but I had to cut down on how many I sold and had to turn a lot of money away.
I bought a few link wheels and pyramid gigs through fiverr, but they proved to be a waste of money. It's another case of quality winning over quantity, and the quality of the links was so bad that they'd usually have a negative result on my rankings.
Total investment - not much, probably about $50 across 4 or 5 sites.
I bought one backlink many moons ago, and I could have gotten it for free, lol. The site is gone now but back then (4 years ago?) it was listed on a popular link selling service. I found an article on the site by looking up the short snippet in Google and then I noticed they had a forum too but that the forum pages weren't available on the link selling service.
I contacted the directly and asked about being mentioned on the index page of the forum and he offered a lifetime spot for $20. I took it. Needless to say I never saw traffic from it and the site was gone less than 6 months later. I wouldn't risk paying for a link again.
I do regularly outsource backlinking, but it's a very risky thing to do. Last year i hired someone to create some backlinks for one of my new project. They used link farming websites, spamming tools and other blasting posts to create backlinks. My website was penalized.
Now i have found a SEO company that i trust and have been using for a while. My new projects go to them.
Really Bauss? From where? And are you going to pay monthly on those?
I do have one experience with backlink buying and I wasn't the buyer. I was approached by someone wanting to buy a link on a specific page with specific anchor text and though I declined the buyer surprised me a great deal. I won't mention names but it was one of the biggest and most well respected SEO sites online, for one of their clients.
Purchasing backlinks is all about quality. DO NOT buy cheap backlinks unless you understand what you are doing. Also, stay away from Fiverr, they do not provide the best quality. Seoclerks and BHW has the best backlinking services in my opinion.
In my opinion buying backlinks is money consuming. You don't know what you are getting and mostly link providers are lazy to offer high quality link and will just automate the process and generate thousands of worthless link farms. I have bought links a several times and you can't get quality links cheaply. Building thousands of quality links to beat your competitors would need an investment worth of hundreds of dollars.
I don't really trust the concept of buying backlinks as I had friends who ruined their rank because of bad backlinks. It also feels like a money sink to me since I can actually build them myself. That way, I feel more safe and I also keep my money in my pocket. I'd recommend learning to build backlinks instead of buying them as it will really benefit you in the long run.