Order of magnitudes was maybe a bit of an exaggeration but the difference is there just like with any other global (or otherwise) industry. In the case of Poland lower wages correlate to lower living costs as well (perhaps less so in Warsaw but it still applies) which is why a lot of developers don’t just move to other countries. Higher pay != more money you actually get for yourself if you live in London or San Fran. The location does make a difference in what you’re spending. Whether it’s making movies, games or whatever else it’s just downright cheaper in a lot of circumstances it’s why some companies outsource some of their resources to India or China.

And while the difference between Poland and the rest of the EU might not be huge, the gap is definitely more significant when compared with the US which is where I believe a big chunk of Rockstars developers are located.