Set a Budget Baseline

The basis used for preparing a budget for an upcoming fiscal year. The baseline budget begins with the current year budget and is adjusted according to actual spending in the current year.

Investment Costs

Fixed costs

These are the one-time costs to launch a community: consultancy, platform development, internal training, etc.

Ongoing resource costs

Maintenance of platform, software licensing fees, hosting, advertising, etc.

Ongoing labor costs

The community management, a percentage of time from other staff members (e.g. management, marketing, etc.).

Overheads

Of course one-off, sunk costs recur again every few years. Websites often need to be redeveloped or adjusted to account for technology changes, changing user habits, best practices, or an array of other reasons (including the whims of executives). This cost is difficult to estimate. For your purposes, divide the cost of the previous platform by the average number of years between community platform redesigns/changes (four years).