"we don't know" is not as good as "we don't know, but it won't be less than the material cost, which is currently X" would go a long way towards taking the people you want to get excited about this product seriously. We understand how "things cost money" works, but going "we don't know, figure it out yourself" is not a nice thing to tell people who are actually interested in what you're making =)

Even updating it to say "it will likely be in the $100-$200 range due to material cost and production fees" is fine: that's a _huge_ range, and still better than "we don't know, figure it out yourself".