Not sure if it would work for you here, but one standard sales technique for this kind of situation goes as follows...
"It's a common question, here is the deal... What you are asking about typically goes from about X to about Y depending on several factors. That's the ballpark range. Once we sit down and dicuss your specific needs, I will come back with # options that have specific costs associated with them and you can see what makes sense for your business. How does that sound?"
Hope this helps and good luck landing the contract,