Quote Originally Posted by Unregistered View Post
It's a 25% increase in the amount of factory builds, which in turn means a 25% increase in your factory 5*s.

Forever.

Compare that one-time cost to blowing 2700 cores on the 3% chance of getting a featured 5* at the store, after which you get nothing.
No idea about others, but I reached 2700 cores near the start of Halloween event and I ended up trading for the guaranteed 5* 3 times instead during that. Sure 5th slot is forever, but as a player who started with launch and has had 4 slots for a long time, I've still only ever made 1 5* from factory.