THIS DATE KEYS?

I never really looked into the "This Date" side event or what not....but I randomly got a key and I was like oh cool this is going to give some some great rewards!

I am so confused. How on earth are you supposed to get 50 This Date tokens when it costs 500 cash to get a single key? The reward isn't all that great, just genuinely curious. 

Also, how do you receive 100 keys? What does it unlock and what is the reward? I posted pics. 

Sorry for the long post. Thanks to anyone and everyone who takes the time to respond!