CD Projekt RED has been steadily updating us on The Witcher 4, which started with a relatively small development team that has gradually grown quite large. Right now, there are many employees working on the game, suggesting that it will ultimately have a remarkably large budget - if you believe one analysis.
The Witcher 3: Wild Hunt has been estimated to have cost $32 million, with $35 million spent on marketing, when development wrapped in 2015. According to an analysis by the Polish Strefa Inwestorów, developing The Witcher 4 will cost roughly $388 million, with a similar amount allocated for marketing.
This means the game's total budget will be close to $800 million. That puts it at over ten times the cost of the previous game in the series, and slightly less than double the estimated $420-$500 million development cost of Cyberpunk 2077 - though that figure also includes patch and DLC development.