Those bags of microwave popcorn are gross, especially the ones with artificial butter flavor. They're also not very cost effective.
But you don't need to buy those bags of microwaveable popcorn. Just put ordinary kernels in a brown paper bag, and microwave. It works very well! I like to season with butter, sea salt, and sometimes nutritional yeast.
EDIT: The seasonings go in after microwaving, and the bag is totally reusable.