Cost Estimate between building types

[StoneCold]

I am building a chemical production building in the US using the 2003 International building codes. I need to estimate the cost difference between a Type 1B building and a Type 2B building. My contractors or A/E firm will not "guess" for me but would be happy to bring two designs forward. Then I can pick one once the designs are done and the costing can be done in detail, but I want to try to avoid paying for a design I have no intention of using.

Any books or suggestions on this? I believe that the cost difference between the two types is large but I don't have any hard numbers to back me up.

Regards
StoneCold