Ideas on cost function [If this is the wrong place to ask this question, please let me know where I can receive better answers:)]

So I'm building an internal tool for an digital media organization. The tool aims to track the number of hours (or any other measure of effort) spent on each brand by different people-roles (Eg: Designers, Content Writers, etc). Using the data collected for the first few months, the organization aims to achieve a better estimate for future quotes given to new clients.

I have thought about the following roles and their metrics:


Designers: Hours
Content Writers: Hours
SEO Guys: Hours
Client-Facing people. (Who actually talk to all the clients): Effort on a scale of 1-10


Whenever somebody starts work on a client (brand), they will start their timer and when done, they'll stop the timer. The tool will log the amount of time spent. Also, the current quotes to the different brands will be entered into the system initially.

I can think about this as a regression problem with the hours put in by different roles as the features and the 'quote' as the output. But I don't think there will be enough data collected in the first 2 months to give a realistic estimate for quotes to new clients.

What can my cost function be?

This will be my first project of this kind. Please give me some ideas. Even new approaches are welcome.

Thanks :)
In that great post, Joel Spolsky use Monte-Carlo simulation to give an estimation of the end of a project.

Thinking about a similar concept whould be to replace the notion of velocity by efficiency.

$$efficiency = \frac{quote}{hours} $$ 

The more discrete the scales of the quotes, the better.

It should work even with a few weeks of data.