I was exactly like you I refuse to spend money on apps really.
But than I won FRINK'S lab with the homer Buddha I got from collecting donuts.
Than I was addicted I got a 15 card. And bought Otto 2 weeks ago
Than got another card yesterday....
The way I look at it as long as you aren't spending massive amount of money on this game like some people in this forum. You are basically just paying for fun. You go to the movies you spend atleast 20 bucks. But in this game you spend 20 bucks and the fun lasts until you are done playing.
This my reasoning but I'm deffly not planning of spending anymore money on this game for a long time.