I think this all depends on the nontechnical cofounder you're dealing with. Some have an idea and just want it built, and, as rcavezza mentioned, have done no customer development. As a nontechnical founder myself, I don't think it's reasonable to start seeking a web consultant or a technical cofounder until a solid amount of work (read a month or two developing the business) has been done. Customer development is only one piece of the pie, but thinking about how the iterations of the product might look, actually designing the site (at the least on a mockup software with the UX clearly defined), and really having understanding of what the consumer wants and rationale for why the product is to work the way it does is all extremely important. A very concrete vision for the product and what future versions of it would look like (contingent upon user feedback and usage, of course) is also crucial. None of that comes in a week of work. It takes lots of time and a huge amount of conversations with users, entrepreneurs, and people who understand the space you're working in.

That said, after that work was done and the nontechnical founder could reasonably say they were ready for their prototype to be built as an MVP, then sure, I'd go with $1000 - 2000 to get it built. Again, to reiterate what others have noted, this depends on the complexity of the product. I don't like the idea of saying "get it done in three days." Too arbitrary. Building a minimum VIABLE product takes communication, and I'm not sure if enough communication would be done in 3 days to actually build something viable.

For those of you that are interested in a JS/jQuery-heavy project with a RoR backend, I am actively looking for someone to help me with this. I have been actually working on this business full time for the last 1.5 months, and I'd like to say I am finally ready to work with someone technical to make this happen. Feel free to contact me @ a[dot]shah811[at]gmail[dot]com