Yes, you are indeed correct. However, it still is all in one car. The ability to have multiple cars use the same device makes the savings huge. Again, it is all a matter of perspective. If one has a gate and a garage, I think adding HomeLink becomes much more understandable; however, for the 15 minutes it took me to set up Tailwind, pretty much the same functionality I would get from HomeLink (I do not have a gate), the price, and ease of use (I do not have to wait for a service appointment, or try to find someone nice or naive enough to set up a HomeLink Module that I bought, I am quite happy with Tailwind.
I will say again, it is definitely a matter of perspective. Some feel the $350 is well worth it, others think it is too much. Some feel the PPF price is well worth and others feel that is too much. To each their own...I am quite happy with my Tailwind, and my wife (in her Model 3) seems to be as well (and for only $10 more dollars (we have iPhones).