Smaller group and often less willing to put out cash for it (besides the few who would be willing to pay substantially more to get great applications on Linux).
https://www.compoundtheory.com/some-arguments-against-linux-...
https://blog.hiri.com/a-year-on-our-experience-launching-a-p...
"Pricing wise, we haven’t noticed anything that distinguishes Linux users from everyone else. They are no more cost conscious than Mac / Windows users. They are definitely willing to pay for software."
As an on-again/off-again linux user, I have paid for software or donated to many projects and it seems others are willing to do the same, however it is still a much much smaller group.