I have a previous version Nuki with a keypad. I think it works great, also locks my door automatically at night. I don’t have it connected to anything else however, to limit attack surfaces. You can still use the app, as it uses bluetooth. That in-app purchase is pretty shitty, though the lock itself is not that expensive compared to competitors. I would advise to search for discount codes or wait for promotions, which happen frequently.
Do remember that it requires a key into the cilinder on the inside, so if you don’t have a double cylinder you can’t use your key on the outside. Which means you can lock yourself out when the batteries die. You should get a cylinder with an emergency function, so you can use a key on one side when a key is present on the other side.
Yeah, charging 50$ to enable hardware they already sold to you is quite something. My model didn’t have that option, it only has a bluetooth radio.
Can’t complain about the build quality though. It’s been rock solid for more than 2 years now, running on 4 rechargeable batteries which seem to last quite long. My first device was from a batch that apparently had radio problems that didn’t affect me, but they replaced it proactively anyway. Can’t really say anything bad about them from personal experience…