Hi Jan,
Yes, we operate one site in particualr which is very successful on behalf of one of our clients. This is based on easysocial but runs several other components. The site has been running for 5 years but we converted from Jomsocial to Easysocial just over a year ago. We have also heavily optimized the site and dedicated server for speed and performance as we have up to 100 users online at any time.
To give you some idea, the site has over 19,000 members, has 120,000 unique hits per month and generates just over $1,400.00 USD in revenue per month. Although the site has around $450,00 USD in overheads per month (mainly server and content distribution costs). However revenue is projected to keep climbing to over $4,000.00 USD per month in the next year. At this point the client will probably sell on the site.
It is very possible to develop a profitable site, but you need a niche and the marketing to build traffic and repeat visitors. Once you have these there are a multitude of options to generate income such as affilaite advertising and direct membership fees. We also alow members to sell directly through the site and take commisions on those transactions.
Hope this helps!