Non-Recurring Fees

[Martin G. Bayerle]

I noticed from the TODO list:

>Implement setup and recurring fees as Safe perl expressions rather than
>numbers, to allow for variable-rate services.  Backwards compatibility is
>obtained because { 43 } in perl is still 43.  :)  Define API to pass
>starting and ending dates and any other necessary data to expression
>(fees are currently evaluated as Safe expressions but more work needs to
>be done to define an opmask for various needs, write examples
>(usage-based billing, etc.) and so on).

How far are we along in implementing non-recurring fees such as one-time 
charges (set-up fees), a single invoice for a used piece of equipment, a 
unique consultation, and usage based billing, eg number of hours use, 
surcharge for disk storage, etc.?

Martin