I second the FB groups; everyone is very forthcoming there and super insightful.
I can share my data it you'd like, but I don't know how useful it'd be. I changed pricing and radically revised my older products a few times, so the sales data is not indicative of what I think most people do on the Guild.
Hi Jürgen, I am a hobbyist producing material for love of the game. I have one adventure (The Beast of Graenseskov) up on DMs Guild. It is about 80 pages and sells for $5, though has been part of a couple sales. It is an “electrum best seller.” My costs in creating the adventure were primarily time writing/cartography/layout, with a few pieces of affordable stock art intermixed with public domain art. Over the course of a year-and-half, it sold 390 copies, grossing $1,846.50, of which Wizards of the Coast & OneBookshelf take 50.00% royalties (not sure how it is split), leaving me with a gross of $923.25.
I’ve heard from other creators who produce material more prolifically, and they have been quite happy with their success on DM’s Guild. I’m noticing the average quality of products improve as DM’s Guild matures, but editing & playtesting continue to be the weakest links in DM’s Guild products I’ve picked up.
Just recently, OneBookshelf opened up DM’s Guild to softcover print on demand (like its sister site DrivethruRPG) though very few creators are yet taking advantage of this.
I haven’t yet had an in-depth discussion with any creators comparing publishing thru DrivethruRPG with publishing thru DM’s Guild, but I think that would be a very interesting comparison as DrivethruRPG has a 20% fee and you can still publish 5e content using material available in the 5e SRD.