Even a billion dollars is crazy money. If you have a company with a subscription service that costs $100 yearly, you have ~2m customers, with a 50% profit margin. Your company makes ~100m every year in profit. Imo that's what is actually worth a billion dollars, maybe even a bit less.
That company is probably worth about $8b, FYI. Obviously that's an estimated average but a P/E ratio of 80 give you that valuation.