Donuts to dollars

Not a chance. You could spend those 600 donuts it would take for 100,000$, and buy vehicles or other items with a 2% or higher bonus and earn more than that in a few days/week. For instance, 15 police cars would cost 600 donuts and get you a 30% extra bonus that is permanent and will keep earning for you, as opposed to a one time cash purchase that will be spent on one building/piece of land. Makes no sense to waste real money on something that's free with a little patience.