re: Business credit card rewards, best card ?

For vendors that charge an additional fee to use a credit card, what would be a threshold to where it would still be a net positive for the rewards that could be earned and utilized personally?

Just thinking, the fee to use a credit card would be deductible business expense, so if you have a vendor charging 2.5% what would be the true cost of that fee when you take into account the reduction in taxable income?

I have been racking my brain on what the threshold would be for paying fees to utilize a credit card and still coming out ahead. Cap one you get 2 points for dollar and each point can easily be redeemed for greater than one cent when utilizing transfer partners.

Anyone ever ran the numbers on something like this?