If a document needs to be developed that requires input from other disciplines_Finance, HR, Property & Facilities, Marketing, Procurement/Supply Chain_ then most likely you are looking at a team building effort to get the job done. In any event, don't look at the task as only as a roadmap that leads to a profitable product or enterprise. Business plans are a great way to build team buy_in, force a thorough review of options, define objectives, establish benchmarks to judge performance, and help arrive at a plan_of_action. Ultimately, it can lead to a Project Management approach to implementing a plan and that can be as involved and detailed as is necessary.
If you said the profit margin would be higher, then you are right. Why would your profit be higher? If you said because of the fixed expenses, you would be right. Your material cost, labor cost, and variable expenses would have gone up 10% but your fixed expenses would have remained the same. You brought in more revenue because of more sales and you spent 10 % more on material, labor, and variable expense to cover the extra sales, but you didn't spend any more on your fixed expenses. So, less overall expenses, would give you higher profit margin. Make sense? So, let's see how we would make a business plan that would show exactly how your business could give you the salary you want.