Okay, first off - this game does not store thing online. The lunchboxes you buy only exist in the .sav files on your device. If it wasn't encrytpted you'd be able to just add a number of boxes by editing a test file and adding a few zeroes to get say a 1000.
So at first it seems that buying anything in this game is a stupid idea, but hey - it is not. Buy things and use them because Bethesda made this awesome game for you and supporting it is a great thing to do.
Then there's the other thing - you pay for actual improvement of your vault so you should get it. Problem is there's very little precautions taken to actually prevent the local data on your device from being lost. There are 3 (yes, three) little files on your device called vault1.sav, vault2.sav and vault3.sav that keep all your vault information in. Damaging these will effectvely delete your vault (or make it inaccessible, which is the same thing) and untl you remove the file that is corrupted you won't be able to start the game too.
This is a bug that was not yet addressed and as such it can be the reason you do not want to spend a dime on the game and want to cheat instead. You'r choice. I choose to spend what I think this game should be worth (which is the equicalent of the largest card pack) and that's it. Funny enough I enjoy playing the vault where I did not buy cards much more, because it all feels more like I earned it. And yah, I am sorta pised that the save that I bought cards in got corrupted when my device ran out of juice, but I hope tha Beth guys will chenge the app to make additional subsequent autosaves, so that automatic backups can be restored ad hoc.
Don't cheat guys. It's a buzzkill.