Many times when responding to a project request you don't have enough information to provide accurate cost and timing, but Upwork requires that you include them when first replying.
Elance allows you to reply to a project and elect to submit cost and timing later.
I think it would be a great thing for Upwork to adopt, especially in light of their new alliance with Elance,
In my opinion it would greatly benefit your users, clients and freelancers alike.
I find that some client's have an unrealistic expectation as to what something should cost, and the it is a mistake to force freelancers to require price and timing before you really understand the scope of a project.
I know that you can revise your proposal, but it has been my experience that doing so can create the appearance of price gouging since an expectation had been set once the initial cost and timing had been provided.
For now, when I respond to any project I always include a paragraph stating that I am required by Upwork to provide and cost and timing but I will need to revisit it if given the opportunity to learn more about the project.
Hope this suggestion gets implemented and I would be interested in seeing if other freelancers feel the same way regarding this issue.
Thank you for your time.