Bob, you certainly raise a number of interesting questions here.
From my experience, the actual hosting part is the easiest to quantify. My company, ZillNet charges about $175 per month for a managed server dedicated to just one customer (basically a leased server colocated at our premises), running OpenACS/Postgres, with 30GB bandwidth included. Others charge more or less than that.
The shared server pricing we are currently in the midst of re-working but the new plan will start at about $20 or $25 per month and include some form of SSL (use your own certificate or use secure.zill.net/yourcompany for free).
Development costs are all over the map. For basic customization with existing functionality, such as stock OACS 4.6 + custom templating (say forums, ecommerce, and one or two other packages) I would not be surprised to see someone offering a menu-priced package(i.e. any three modules) for about $1000. For more than that, expect development costs to grow steeply.
Oracle seems to add to the pricing a multiple from 2 to 4 times in terms of hosting charges; but I would not expect developing an Oracle-only package to cost much more than a Postgres-only package.
dotLRN and dotWRK are too new to see much data on, yet.
Overall, I feel that as the toolkit progresses the cost of getting a basic site up and running will decrease due to templating cleanup alone.
