Yes, site sponsors pay for the privilege of advertising on pipesmagazine.com. Like any other business, we receive monthly, quarterly or yearly invoices (depending on sponsor payment preference), to pay from.
I can't speak for any of the other site sponsors, but I do like it when someone accesses my website by clicking through from my pipesmagazine.com ad's website address link. My website has a couple of different options that I use that shows me the various ways that customers access the site, including the weekly number of click through's (direct access) from my ad on pipesmagazine.com.
And, now would be a good time to once again say how much I appreciate the business I get from many of our members here!