The average game developer in Istanbul (similar to Ankara) makes about 60 Turkish Lira an hour, which equates to about 7.05 USD, with an average pay of 125,000 Lira per year (about 14,500 USD). There are 131 employees at Taleworlds as of 2020. Therefore, the employee pay would be roughly 1,899,500 USD, probably a little less or more based on currency exchanges. Overhead is somewhat difficult to calculate, but I would put their facility costs (With electricity, which is cheap in Turkey) is probably around 5,000 a month, that is just a rough estimate based on how many employees they have and how much square footage they would need. So, overhead would be roughly 60,000 USD a year. Add these two together and you get a little under 2 million USD per year. This is a rough estimate, it is probably less than that due to the fact that they probably pay less than the average because that is based on a lot of experience.
Bannerlord has sold between 3-5 million copies, according to steamdb and steamspy. At an average price of $45 (it depends on region, some places sell for less, some like pound and euro sell for more), after Steam's 30% cut, this leaves Taleworlds with roughly $31.50 for each sale. With 4 million sales on average, Taleworlds has made, should my calculations be correct, roughly $126,000,000. Bannerlord has been in development since 2012 as far as we know, lets give them 2 years pre-announcement of development, which equals 11 years. Assuming 100% of their time at Taleworlds was devoted to Bannerlord (which it wasn't, warband was still in development well during this time period), this means that 22 million dollars was spent to get 126,000,000, which equates to a profit of a little over 100 million dollars, over 5X a return. I may have gotten some calculations wrong along the way, and I may have estimated poorly, but no matter what, that is a lot of profit for the garbage can/excuse for a game that we got.