I think that the currency values definitely need to be tweaked. The rate at which the game expects you to spend viagra greatly exceeds the rate at which you can actually get viagra. And they also need to make it so that you can choose to go back to a previously cleared difficulty level if you want. If the game gets too hard, you should be able to choose to go back to an easier difficulty and grind it until you get strong enough to tackle the new level. But you can't really do that if the game forcefully increases the difficulty level each time you clear something.