Here are a few resources that can be useful in estimating costs for ID projects.
Estimating Costs and Time in Instructional Design. This article provides a comprehensive analysis of factors to consider when developing your training budget, along with examples and a case study. I particularly like the table with percentages of time for each training development task, for example, the percent of time allocated to develop the analysis of the lesson versus the prototype of the lesson.
Time to Develop One Hour of Training – I find this article helpful for its identification of factors that can reduce instructional development time. I also like the survey results chart that breaks down training hours estimates into various categories; such as, level of interactivity in a web based instruction from limited to high interactivity, and each with its own estimation of development hours.
Why eLearning Development Ratios Can be Hazardous to Your Career – This is a great article that advises caution in using e-learning development hour ratios, and discusses factors you need to consider.