Dealer fees are calculated to be a percentage of the total cost including the fees, not as a percentage of the system cost alone. Instead of taking the Total System Cost Amount and multiplying by the dealer fee, it is instead calculated as such: Total Cost with Fees = System Cost/(1 - dealer fee percentage), where the dealer fee percentage is between 0 and 1. Dealer Fee = Total Cost with Fees - System Cost.
As an example: If a dealer fee is 24.79% (represented as 0.2479) and the System Cost is $25,967.50 then the math is: $25,967.50 / (1-0.2479), or $25,967.50/ 0.7521 which equals $34,526.66. Dealer Fees in this example come up as $34,526.66 (Total Cost with Fees) - $25,967.50 (System Cost) = $8,559.16
It's done this way because the fees have to get tagged onto the principal that is being financed.