Whilst I don't know the exact statistics of what each item costs for each business, I can tell you that the pricing structures effectively work "backwards" during the middle point.
By this I mean that items such as the Oil Company will be cheaper to upgrade than the same level of the Newspaper Delivery business. The amount of profit produced by the Oil Company (assuming you have the speeds upgraded which happens with Upgrades and each 100 levels until it doubles profit) will be greater than the lower level businesses.
This does, at around level 2000, actually change a little and the Newspaper Company ends up producing more profit than the Oil Company but still costs more for each upgrade. To try and illustrate it I've included a picture from my own game. As you can see the Newspaper Company makes a lot more profit than the Oil Company, but still costs more to purchase new businesses.
I know this from spending over 60 hours playing it.