About to enter this arena myself... I have several modules that I would like for personal use and plan on making them available.  I completely agree with your frustrations and some of the other developer's comments here.  I'd like to place my own spin on things just from my own perspective:

Most module developers probably work full-time somewhere else except for the really big shops that are consultants in their own right.  Holding down a full-time job, they are tied to the rigors and responsibilities of that job first, before they have any time to dedicate to their "side-jobs".  Myself, I work full-time as a software engineer developing web applications, windows applications, server applications, etc and then when I go home, I put on my consultant hat and work another 10-20 hours per week as a software consultant.  On top of that, I'm a husband and father and try really hard to be there for my family.

These developers probably created a module for their own use or for the company they worked for and thought, "hey, this is pretty snazzy... maybe somebody else will want to buy it."  Unfortunately, as you've stated in a sense, they don't think about the customer.  They think they can release it, charge for it, and forget about it.  I've been in your shoes where I have some modules that absolutely suck and never hear back from the developer, so I end up just junking it.  I've also had experience where the developer was quick to answer.

On that same note, I believe the whole DNN community is like this in general.  Sometimes people make posts to the forums and never get an answer, yet other times you have an answer as quick as you post. 

I personally make myself available to all my clients whenever they have problems and feel like I'm very good at responding to their needs.  I agree with you that, in the least, the developer should say "i'll look at it and get back to you."  I hope that when I get around to releasing my own custom modules I won't be one of the many who release, take the money, and run.

Sorry for jumping all around here, but just presenting the many facets that *could* possibly be coming into play.

I do want to make note of some stand up guys by name.

John Mitchell has been extremely helpful with general DNN questions I have had even though I am not a paid customer..... yet.

Scott McCulloch at Ventrian is awesome. He is a little slow to respond at times, but be patient... he will get to you. I am currently working with him on developing a custom module for my website. Great Aussie!

And the latest addition to my list is Will Morganweck at Active Modules. I had a small problem when upgrading, and even though the site has M-F business hours, he emailed me with his mobile number on a Saturday and we fixed the problem. Stand up dude!