a simple solution would be to add an extra "0" onto the winnings. In other words, instead of earning $900 million from a boss battle, I'd win $9 billion from a boss battle. While it would allow me to start purchasing the units I need, I wouldn't have a massive influx of cash. Just enough to get me started on building an army, make the game fun because of the income, and add some excitement.

You all moved the decimal point over several places too far on the winnings. Try moving it back one place in the other direction.