Why do you need to know these percentages? As your sales increases or decreases, your material cost, labor cost, and variable expenses will track accordingly. They will track very close to the same % as your current business. As an example, let's say your current sales is averaging 贄ꯠ per month and your material cost is averaging ฤꯠ per month. That's 20% of your sales (ฤꯠ ÷ 贄ꯠ = 20%). So, what would your material cost be if your sales were averaging 赨ꯠ per month? It would still be 20% but it would be 20% of 赨ꯠ or ุꯠ. So with these percentages, you can project your material, labor and variable expenses. See how it works?
Besides, your friends may be 100% behind you in your new venture, but, in case you are hoping to involve others who have actual money to invest, you may need to be able to make a convincing case. Wouldn't it be nice to have anticipated possible questions and be ready with plausible answers? If you are risking your own money, that is perhaps even a stronger reason to do some indispensable planning.