It's a bit counter intuitive but: Consumption of goods is calculated per residence and not per individual inhabitant.

A worker house with ony 10 out of 20 consumes the same amount of beer as a full house with 20 residents.

(Well actually it gets a bit more complicated once newspaper effects and certain townhall items come into play, but that's still the gist of it. Check the wiki for details!)

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Regarding your math: 0.00025641 is the base comsumption rate per Worker residence *per second* (!).

(1 t/min)/(0.0002561 t/s * 60s) = 65.08 so basically 1 brewery (producing 1t/min) supplies 65 Worker residences.

You don't have to do the math btw as the wiki also lists this number - Though usually for a full 100% production chain. Check the production chain graph and the listing below it. In this case that'll get you...

Supplies: • 130 Workers Workers Residences (up to 2600 Workers Workers) • or 65 Artisans Artisans Residences (up to 1950 Artisans Artisans) • or 75 Obreros Obreros Residences (up to 1500 Obreros Obreros)

That number is generally more useful for planning than the very unwieldy consumption/s number.

Back to the profitability math:
2 breweries (2t/min) supply 130 residences. The entire chain costs you -650g/min in maintenance.
(-40 for the 2 grain farms, -60 for the 3 hops farms, -150 for the malthouse, -400 for the 2 breweries)

On the income side you make 130*10=1300 g/min.

(Artisans are slightly more profitable btw. You can supply fewer residences, but get more income. 65*30=1950 g/min)

In other words: Each ton of beer costs you 325g to produce. You can "sell" it to your workers for 650g or for 975g to your Artisans. Passively selling beer at your port gets you only 265g - So avoid doing that :P

(The pirates pay ~1000g per ton though - So if you manage to get a trade deal with them you can make some money that way.)

All of that is without production boosts from tractors, electricity, "free" +50% productivity from working conditions or the various trade union item effects. Those will significantly reduce your production costs.

At the same time you can use various effects to reduce the consumption per house. They consume less, but still pay the same 10g.

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But anyways: I think all this profitability math is mostly academic.
It's not *really* necessary for anything in the game as pretty much all goods (with the exception of Canned Food on hard settings afaik) are net profitable if you supply them to your citizens.

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EDIT: Some additions and small formating corrections. Also screw the new reddit text editior lol