A simple but effective comparison between an expensive filter pod and an inexpensive filter pod is shown in this video. The comparison of the pods is rated according to their quality and set-up. It goes without saying that for the pods with better quality, you will have to pay way more than you would for the filter pods with poorer quality.
In the video, the feel of the filter pods is given. The more expensive pods are more firm and rigid, which gives you the confidence that the pod is a solid one and will do its job well.
On the other hand, the cheaper filter pod is flimsy to the touch and the material is soft. Although both pods are aesthetically pleasing to look at, their build separates them completely.
The video shows how the cheaper filter pod does not provide a secure rubber boot and that means that air will easily make its way through that which the opposite of what you should want. Expensive pods are more secure air filter pods for they have secure rubber molds wrapped around them.