I doubt this had little to do with any relationship between linux users and their likelihood of overpaying on a hotel room or rental car.

The price paid by Linux users was almost certainly bumped up by Linux gamers explicitly trying to support game studios who supported Linux.

You wouldn't see the same thing with hotel rooms or most other products that weren't intimately tied to the OS itself.

Yeah, there was (or is) a inverse correlation between how common an OS is on the desktop (Windows, Mac OS, GNU/Linux; starting with the most common OS) and the amount people are willing to pay for a HumbleIndieBundle release.

This is presumably partly because customers appreciate that game studios see their chosen OS as a viable release target.