Maybe this is a bit rant-y, but "Paid Fairly" is incredibly relative. Every time I've been asked about doing some sort of paid coding assignment in my free time, I've asked to be paid at my hourly consulting rate, which many people do regularly, which is $60/hr. This is really not that much for a consulting developer.
Every time this has come up, the company would not pay that rate, and offered something more like $20/hr.
It is just insane to me that if you are interviewing me for a position which makes $105,000 a year and cannot offer even close to equivalent compensation for the interview.