Opening note: I have only been a patron of the Empire of the Ghouls adventure, so all of my comments relate to that experience.
This may have already been covered (I haven't read the whole thread), but I the opening poster is trying to compare an Open Design patronage project with a normal adventure you would buy as a PDF or hard copy.
To me they are very different items. Generally when you buy a normal adventure you don't get access to the adventure writer to ask him questions about the adventure (i.e. what did you mean by this?, is this meant to work like this?, is this an error or have I missed something? etc.). And you certainly don't get to ask those questions while the adventure is being written.
On top of that, I found that essays and advice that Wolfgang posted while he was writing the adventure were also part of the package that I was paying for. It was like getting several columns of Dungeoncraft included with the adventure, with the plus being that you got to choose what those columns were about and they were usually related back to the adventure at hand.
The other bonus was being able to discuss the adventure with other people, allowing you to bounce ideas off of them (or just steal them!

) for when you ran the adventure in your own campaign. Sure, you could do this with a normal adventure. Just post a thread about it on EN World. However, with the Open Design project you knew that the people on there were definitely interested in the adventure and knew what you were talking about. So the signal to noise ratio was a lot higher.
Overall I definitely felt like it was worth the cost. If you are just after an adventure I don't know if you would get your money's worth from it. And, more to the point, the adventure you get at the end is only a part of what an Open Design project is all about. The actual designing and creation of the adventure itself is a big part of Open Design. Some would even argue that it is really the main part.
Olaf the Stout