As previously mentioned, Mobdro is a completely free app. However, as with many other apps out there, there is a premium version that you can pay for that allows the user to enjoy Mobdro without being inundated with the unseemly apps.
You may upgrade to premium at any time after downloading the free version and this option costs about $3.55. There have been some reports that a premium version is no longer available, but some users believe it is a temporary glitch. Either way, users were happy to pay that monthly premium to allow for a much more user-friendly and ad-free experience.