With mojoPortal you would have a designer create a design and then you would need to translate that into a mojoPortal skin using the various files that make up a mojoPortal skin:
layout.Master, theme.skin, style.css and other supporting css and image files. (located under Data/Sites/[SiteID]/skins/skinname)
You don't need a designer to be involved in designing every page of the site just one good design which can be translated to a mojoportal skin by someone with an understanding of css. You could create a few different skins as you can have specific skins assigned to different pages but you certainly wouldn't need 250 different skins. You can also optionally allow users to pick a skin that they prefer.
The 250 pages of content can all live in the database and be created/edited by users with no help from developers or designers
All content pages for mojoportal come from the database and can be edited in the browser by user's with permissions. Permissions are configured by roles and you can add as many roles as you need. You can create pages in the browser and add feature modules to the page (Html, Blog, Forum Gallery, etc) and user's with permission can edit the content in these feature modules using the same WYSWYG editor that you used to post in this forum. Users don't use C# to edit content, I can't imagine that. There is no need for place holders either, users can edit using the editor. Style is separated from content so style can be changed independent of content by changing the skin.
To get an idea of what you can do with mojoPortal, try the online demo
http://demo.mojoportal.com which allows you to login as administrator and create pages and edit content yourself.
Hope it helps,
Joe