Taxes are payed on net income not on individual transactions (barring sales tax).
If I make $100 in a year and spend $1000 that year, my income is ($900). How can I spend $1000? Generally through loans and bonds. How do I secure said loans? Generally simply by showing how much VC and income comes in with a business plan that banks accept.
But that's the secret to the money flow. That's also partially why the collapse of SVB was such a blow to the tech industry. A LOT of loans were issued by them.
Revenue. Your $20/month is going on the revenue line of accounting. The income line on the accounting can be negative despite your generous $20 donation.
Where is my $20/month for GPT-4 going then?