2022 : Vuforia is free
Vuforia Engine is an Augmented Reality Software suite (from PTC). The Vuforia Engine SDK is now free for commercial purposes unless you want to use Model Targets or Area Targets. Even watermark is not set in the basic plan (free) for the following AR targets : Image, VuMarks, Multi-Targets, Cylinder, Ground Plane.
It is interesting to look at the new Model Targets since it can track models using 3D scans (photogrammetry or iOS scans using dedicated apps) or 3D CAO models as inputs. It seems way to acquire the tracked models is changing in AR SDK !
More information about the Model Targets : click here