Are DNN modules underpriced? Yes. And No. I don't care if a module for displaying Google adsense is only $10, add a Text/HTML module and paste in the Google code and you're done. That $10 is a waste. Would a full-featured content magamanet system be worth $5,000? To many buyers the answer is yes. This assumes support, training and a workable intuitive interface for end users existed, versioning and approval systems were in place and that the product accepted Word, Excel, etc. content and automatically converted it to properly formatted HTML or a PDF file that could be served. A very sophisticated WYSIWYG editor and simple page management functions included. There really isn't such a thing for DNN, yet, though some come close. That's why many of the CMS modules are a bit pricey.
How do you price a module? Ideallly, the same way any product or service ie priced. Mark up the cost of producing the module by a percentage necessary to generate the profit needed to sustain the producer of the module. Sure, a producer could be in a mud hut just outside the capital of Elbonia, or they could be in a Silicon Valley high-rise. Costs will vary for the production, and the Elbonian product should probably be cheaper due to lower production costs.
Few DNN module developers are professional software companies. As more develop, the pricing will fall in line. Currently, the higher-end customers are served by integrators who use DNN as part of the solution. Those are the guys with the pricing designed to earn a decent living. The mom and pop shops, or in many cases just pop, don't have the ability to provide the support, the customization, the documentation, the error checking, beta testing and release process needed to justify a higher cost.
And to a certain extent, the lack of a comprehensive package of modules to provide a specific vertical market solution makes DNN less desireable than a Community Server setup. And thus worth less in the market place.
Jeff
PS: Don't go raising porices on us though, just because you aren't in Elbonia... :)