Here are a few signs that developers spend time and effort building and maintaining their extensions:
It takes time and money to develop a well coded extension and provide best-in-class support. With low price extensions you risk two things:
Magento Marketplace’s process for accepting extensions is fairly rigorous, meaning that the code is checked before it’s approved to be sold on the site.
Coming up with a question to ask the extension provider is the best way to get a feel for how responsive they are and how they deal with support. The response you get i.e. how quickly, politely and accurately it’s answered – or even if it’s answered, can sometimes tell you more than a review might.
Members are selected on their customer service processes, the quality of their code and their motivation to innovate and collaborate with other extension providers in order to provide the best experience to Magento merchants.