Yes, every weapon returns more money than you spend on it, so you can progress further. But with bombs, if you get only one rat with it, it will pay less money than you spend and gradually earns more if you can manage to terminate more rats with a single bomb usage. This is to make it harder to use, as it is extremely powerful. I made a new version of the game, with a test mode with more money, so you can play with it a litte more without need to play from start. Thanks for playing my game, really appreciate your feedback!