TypicalDutch

That is pretty much how it is, except for salaries.The team consists of volunteers. But indeed, the generation of voices, and there are a lot, and the backend infrastructure consume the rest of the cost.

[...] Reduzierung der monatlichen Nutzungskosten auf 15 Dollar zu erwarten, wie Brian im Video erklärt [...] Yeah that is a big misinterpretation of what Brian actually said in the video.

No, that wasn't said on the video. Brian specifically talks about pricing and what the 50% price drop of OpenAI means for SayIntentions. Yes it means that price will drop (significantly) but OpenAI is only part (~50%) of the logic behind SI. So where ever you read the $30 > $15 drop, it's not coming from SayIntentions itself.