That seems like a good starting point. With these numbers, you're not more than a couple hundred pounds different in grist. Good enough for estimates.
In brewing, most of your profit is made and lost in efficiencies that have nothing to do with wort production. Simple things like steam and glycol chiller capacity, floorspace, drains and access for trucks will be "hidden" beer costs that add up to much more than ingredients.
Whatever your plan, if you pay up front for growth and minimal labor needs, you'll reach profitability much sooner. I.E. Sloping floors for good drainage can save 2 hrs of labor to squeegee, every day. With taxes, that labor is around $12,000 a year. Time much better spent on filling kegs!
Same with investing in a 4 head, automated keg washer. You think you won't need it now, but it frees you up to do something else, without having to monitor it.
Maybe I sound like a curmudgeon in these posts. Sorry. I just hate to see a lot of enthusiasm and inspiration killed by poor planning. I just read about a respected, award winning brewery who will be shutting down at the end of this month. This despite 58% growth in the last two years. Why? They went cheap and have virtually no automation. This means margins so thin that they can't afford to reinvest, much less handle a rent increase or rise in minimum wage.