On every[0] Humble Bundle so far, the highest average donations come from Linux users.
On some, they've even donated the same amount or more in total dollars compared to OS X users - ie, Linux users have been more profitable even though they have a much smaller market share.
In short, Linux users are very profitable (per-user).
[0] I can't confirm that it's 100%, but it's been every Humble Bundle I've participated in (a lot), which I think is a large enough sample size for the purposes of this statement.
I think this is partly caused by the lack of offering. For instance: I'm throwing a lot of money at Steam and Valve for the games that are available there because it is one of the very few vendors that has native games for my platform.
When you use a lot of FOSS, I think (at least for myself) I tend to pick my spots to get closed-source, for-cost software. If it'll run well on my platform, and I like the organization developing it, it feels more like... monetary collaboration, say, than simply buying another thing. If you're used to buying all your software, paying the minimum might look like just the (perfectly reasonable) cheapest way to get it?
Not to suggest that there actually IS any difference between the two groups when they pay - I just feel like more a good-deed-doing partner when I voluntarily pay more for something like humble bundle, that's all. It's silly and false, but it's definitely a feeling.
Or developers appreciate the effort it takes to program something, and want to break away from the 99c per app approach and want to make a more fair payment?
My gut feeling is that someone running Linux as their desktop OS has had to opt in; this means that the pool of potential desktop Linux game purchasers is more likely to be made up of people who are motivated by Linux itself; and that these people are thus more likely to be people who are invested in the success of Linux as an environment.
I'm not au courant with Linux in any of its various forms, so my assumptions above could be wildly wrong, of course.
> ... these people are thus more likely to be people who are invested in the success of Linux as an environment.
I think that you are correct -- at least in part.
I have zero desire to play games but I have purchased many of the Humble Bundles, for example, simply to "support the cause" and encourage other vendors to also consider Linux as a viable platform. I usually give away whatever it is that I've bought.
On some, they've even donated the same amount or more in total dollars compared to OS X users - ie, Linux users have been more profitable even though they have a much smaller market share.
In short, Linux users are very profitable (per-user).
[0] I can't confirm that it's 100%, but it's been every Humble Bundle I've participated in (a lot), which I think is a large enough sample size for the purposes of this statement.