Yo, these guys spent their own personal time and resources developing a game that is graphically pleasing and enjoyable (Even for an Idle Clicker)! Heaven forbid they are looking for some way to profit from their hours of work and creativity..... Like seriously guys.... If you've ever spent even 3 hours working on any project, you too would want appreciation for that effort, and what shows appreciation better than a lil extra cash in the pocket?
They made an avenue for the Free players to also gain unlockables, and shooting them the same price for a Big Mac isn't going to shame you any.