Excel Formulae - returning a zero value

Hello,

I'm trying to set up an excel quotation sheet using the following formulae

=SUM(B6*C6)+(D6*$E$3/1000)

Cell E6 = the quantity
Cell B6 = This is a manual import and can be either zero, or 1, 2, 3, 4 etch
Cell C6 = This is a static set up cost
Cell D6 = This is a cost per thousand

So for example:
(1*£250)+(£1*100,000/1,000) returns a correct cost of £350.00 (in cell E6)

The problem I'm trying to solve is that when I put in a zero in cell B6 - I want the total in E6 to also return a value of £0.00....however it still picks up static set up cost of £250.00

Any ideas please?

thanks very much