I work in a different, but related industry, so I can relate to the issues and concerns on pricing.

I'd suggest that everything takes 2-4 times as long as you might think at first. I'd suggest going in at maybe 3x your best guess. You will probably have to justify this to your client. Explain that you are accounting for all the little things that can be difficult and suck time. Explain that you have accounted for this up-front based on your experience, and also explain how you are providing a premium service. Be sure to follow-through with the premium service by going above and beyond.