If you are client-facing consultant, your billable rate is paying:
- Your salary
- Your benefits
- Your expenses (travel, per diem, equipment, software, anything else)
- And then... Salary, benefits, expenses of all your NON-client-facing teammates: Salespeople, marketing, management, client relationship, administrative, HR, etc.
So as a consultant, you are the product, and as such have to be sold at a price that nets enough profit to pay for rest of the organization.
Normally when they say "you cost $150/hour", what they mean is, "you, and all the support framework behind you, needs to be billed at $150/hour to pay off".
Hope that helps. If you're in-house developer and not client-facing, it's harder to understand and justify cost figures, but typically would be nowhere near that rate...