The drone doesn't look that difficult to make, it's just two GPS units, wireless communications, a bit of math. Three years and $15 million should easily have covered it.
There are lots of interesting problems. Even the big competitor DJI with its Phantoms didn't get it 100% right, like if there are some leaves in the way when the drone follows you, the props will try to do some garden work on it. And sometimes it loses you. But works pretty good in an open environment with no trees or other obstacles. There are some videos of it following a car.
It is a bit simpler for the Lily drone to follow you, because of the tracking device, but still complicated enough. And as I read on the webpage, no mechanical camera gimbal. This won't work for high quality videos.
You're right, the quality wouldn't be 4K Ultra Mega Maxi Super Turbo HD like a Phantom with a gimbal and a GoPro, but using using a FishEye lens and doing pan/tilt in software can be surprisingly effective. I've got a Parrot Bebop and the video quality is alright.
The other advantage to a software gimbal is no moving parts, which makes the drone lighter and much more robust. Also a lot cheaper, too.
I've crashed mine a number of times (owing to inexplicable disconnects which I think I've finally fixed), one of the crashes involved it automatically "returning home" after a disconnect. Unfortunate home turned out to be some pine trees on the edge of a field, where I had taken off from. It gracefully flew back, but because the GPS didn't have a full 3D fix when I took off, it overshot by about 10m, putting it right over said trees where it started to descend, then hit every branch on the way down. The only thing that broke was one of the plastic feet. I'm glad the return to home feature worked, because when I initially lost control of it, it was hovering 200ft over a pond!