Probably due to rounding? If any of those values are from variables or fields then possibly one or more are accurate to more than 2 decimal places. If they are all typed in, then I have no other idea except to suspect some code or other factor is affecting the output.
I presume you're saying the above calculation is what the answer should be and that answer is $489,838.00 not $439.838.00
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.