The IDE is called RStudio, not R-Studio. IDE is for R, and there is nothing inherently unique to that IDE. R-Studio on the other hand is a tool with absolutely no competition for over a decade, and is thus worth as a paid tool for all OSes.
When I used it on Windows, I pirated it. But there exists no way to pirate it on Linux, and when I have enough funds, I will ensure to buy something as useful and irreplaceable as R-Studio, since I get the liberty to use it on any OS.
Also only the Network Technician license costs $800. Regular single user lifetime license costs around $70 and works offline.