@renchap Generally I expect contributions would be a labor of love. But also the work that is put into supporting ActivityPub apps can also be used to give talks at meetups and conferences. The maker of @IceCubesApp has done this and shared all of the code on GitHub. I am sure he can leverage that work when setting pricing with clients or negotiating an offer with an employer.
Personally I have a monthly donation going to my server hosts. I'd like all server hosts to pool part of their donations to fund a core team which can dedicate time toward completing features and fixing bugs which are the highest priority to the community. And I'd be happy to kick in donations to this effort.