I have been reading recently about developers giving realistic timescales to deliver projects in. I am well aware that developers can over and under estimate projects and also that you can spend a lot of time developing a project only for the idea to be changed just before the site is ready to be released. However with this in mind here is my Drupal migration timescale equation:
D + 12 + P + F = H
We of course that is not the final word on the matter, as letters in equations mean nothing without explanation. I have reduced the size of this equation from:
D + 2 + 10 + (P * 0.33) + (P * 0.33) + F + (P * 0.33)
Design can take as long as it requires for a design to be created and agreed on. Largely this can be undertaken by either a separate designer/graphic designer or the developer/designer themselves. Obviously this stage is an important factor of development, however, it can be done concurrently to inserting the data reducing the amount of time overall.
The 2 is equivalent to installing and setting up a basic Drupal installation on your server/hosting provider. This can be flexible, but it should be completed well within 2 hours.
The 10 is equivalent to the time taking to translate a design into a theme that can be used in Drupal. This is an approximate timescale, however, if you have a well designed Photoshop image, you should be able to break it up into a html/css drupal theme within 10 hours
F = Features. If you are looking at any site you can probably pick up any number of features that you require. For a basic site features may be completed within a few hours, however, a large/complex amount of features can take a long time. The features however, can be worked out and decided upon.
P = Pages. The first P is for insertion of pages. The second for constructing the information architecture, the third for editing post delivery. This is an approximate estimate, but you should be able to complete most of the migration of 1 page in 1 hour.
A simple blog may have 50 pages and simple features.
Therefore following the equation:
5 + 12 + 50 + 5 = 70 hours migration! Wooo 2 weeks!
A more advanced news site with 1000 pages and more advanced features.
Therefore following the equation: 40 + 12 + 1000 + 100 = 1152 hours! 1 dev = 28.8 weeks - Blimey thats a lot!
Anyway, hope this might be helpful to Drupal project managers. I would expect that this will change substantially over time.