Some calculations. Others have posted that the multipliers for the different resources are different. Lemonade is the perennial cheapie. It has the lowest multiplier (1.07) and the lowest starting price ($4). It also starts at level 1 so it has another small advantage (technically you've already invested just under $3.74 to get your first lemonade stand).
As for the others the starting prices consistently rise (no duh!) but the multiplier consistently drops. Newspaper is 1.15, Car Wash is 1.14, and so on down to the oil company which is 1.07 again. All this means that as you buy more of each resource the price of the more expensive resources goes up by a smaller percentage and eventually the cheaper resources will become the more expensive ones but without the added benefit of bringing in more money. People have noted this with the Newspaper being the most expensive once you get to level 300.
Loving Swarm Assault 1 with the auto-magnet ... all those bunnies with nothing to show for all their hard work. Then, once they're all on board ... WHOOOOOOP ... incoming nuclear strike...
 "AdVenture Capitalist"){kind=icon}
 "Tactical Assassin 2"){kind=icon}
 "Caribbean Admiral"){kind=icon}
 "Mushroom Madness 3"){kind=icon}