I am reminded of the free software / shareware debates of my youth. If something betters humanity, shouldn’t it be free? If something makes your life better, isn’t it worth paying for?
I won’t (probably) add a “tip jar” to my stuff, not because I don’t think my stuff has no value, but because the payment to me comes from hearts, highlights, and sweet/complimentary/smartass comments left. Also: we don’t need the money.
Others do, I understand, so I am also inclined to drop a ten spot into a virtual jar on occasion. Also: we check out Kickstarter for kids’ books getting started out that we can sponsor.